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15030 commits

Author SHA1 Message Date
Mateusz Guzik
61852185ba locks: change sleep_cnt and spin_cnt types to u_int
Both variables are uint64_t, but they only count spins or sleeps.
All reasonable values which we can get here comfortably hit in 32-bit range.

Suggested by: kib
MFC after:	1 week
2016-07-31 12:11:55 +00:00
Mateusz Guzik
e0c45af904 sx: increment spin_cnt before cpu_spinwait in xlock
The change is a no-op only done for consistency with the rest of the file.
2016-07-30 22:23:31 +00:00
Mateusz Guzik
7a54be1870 rwlock: s/READER/WRITER/ in wlock lockstat annotation 2016-07-30 22:21:48 +00:00
Konstantin Belousov
50c22263bb Cache getbintime(9) answer in timehands, similarly to getnanotime(9)
and getmicrotime(9).

Suggested and reviewed by:	bde (previous version)
Sponsored by:	The FreeBSD Foundation
MFC after:	1 month
2016-07-30 09:25:57 +00:00
John Baldwin
e2325d8285 Don't treat NOCPU as a valid CPU to CPU_ISSET.
If a thread is created bound to a cpuset it might already be bound before
it's very first timeslice, and td_lastcpu will be NOCPU in that case.

MFC after:	1 week
2016-07-29 20:19:14 +00:00
John Baldwin
005ce8e4e6 Fix locking issues with aio_fsync().
- Use correct lock in aio_cancel_sync when dequeueing job.
- Add _locked variants of aio_set/clear_cancel_function and use those
  to avoid lock recursion when adding and removing fsync jobs to the
  per-process sync queue.
- While here, add a basic test for aio_fsync().

PR:		211390
Reported by:	Randy Westlund <rwestlun@gmail.com>
MFC after:	1 week
Sponsored by:	Chelsio Communications
Differential Revision:	https://reviews.freebsd.org/D7339
2016-07-29 18:26:15 +00:00
Brooks Davis
40018b91dd Don't create pointless backups of generated files in "make sysent".
Any sensible workflow will include a revision control system from which
to restore the old files if required.  In normal usage, developers just
have to clean up the mess.

Reviewed by:	jhb
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D7353
2016-07-28 21:29:04 +00:00
Ed Schouten
5590eb985e Regenerate system call table for r303435. 2016-07-28 12:22:34 +00:00
Ed Schouten
d9c4cd2fbc Change the return type of msgrcv() to ssize_t as required by POSIX.
It looks like the msgrcv() system call is already written in such a way
that the size is internally computed as a size_t and written into all of
td_retval[0]. This means that it is effectively already returning
ssize_t. It's just that the userspace prototype doesn't match up.
2016-07-28 12:22:01 +00:00
Konstantin Belousov
2d19b736ed Rewrite subr_sleepqueue.c use of callouts to not depend on the
specifics of callout KPI.  Esp., do not depend on the exact interface
of callout_stop(9) return values.

The main change is that instead of requiring precise callouts, code
maintains absolute time to wake up.  Callouts now should ensure that a
wake occurs at the requested moment, but we can tolerate both run-away
callout, and callout_stop(9) lying about running callout either way.

As consequence, it removes the constant source of the bugs where
sleepq_check_timeout() causes uninterruptible thread state where the
thread is detached from CPU, see e.g. r234952 and r296320.

Patch also removes dual meaning of the TDF_TIMEOUT flag, making code
(IMO much) simpler to reason about.

Tested by:	pho
Reviewed by:	jhb
Sponsored by:	The FreeBSD Foundation
MFC after:	1 month
Differential revision:	https://reviews.freebsd.org/D7137
2016-07-28 09:09:55 +00:00
Konstantin Belousov
a9e182e895 Extract the calculation of the callout fire time into the new function
callout_when(9).  See the man page update for the description of the
intended use.

Tested by:	pho
Reviewed by:	jhb, bjk (man page updates)
Sponsored by:	The FreeBSD Foundation
MFC after:	1 month
X-Differential revision:	https://reviews.freebsd.org/D7137
2016-07-28 08:57:01 +00:00
Konstantin Belousov
b7a25e63b6 When a debugger attaches to the process, SIGSTOP is sent to the
target.  Due to a way issignal() selects the next signal to deliver
and report, if the simultaneous or already pending another signal
exists, that signal might be reported by the next waitpid(2) call.
This causes minor annoyance for debuggers, which must be prepared to
take any signal as the first event, then filter SIGSTOP later.

More importantly, for tools like gcore(1), which attach and then
detach without processing events, SIGSTOP might leak to be delivered
after PT_DETACH.  This results in the process being unintentionally
stopped after detach, which is fatal for automatic tools.

The solution is to force SIGSTOP to be the first signal reported after
the attach.  Attach code is modified to set P2_PTRACE_FSTP to indicate
that the attaching ritual was not yet finished, and issignal() prefers
SIGSTOP in that condition.  Also, the thread which handles
P2_PTRACE_FSTP is made to guarantee to own p_xthread during the first
waitpid(2).  All that ensures that SIGSTOP is consumed first.

Additionally, if P2_PTRACE_FSTP is still set on detach, which means
that waitpid(2) was not called at all, SIGSTOP is removed from the
queue, ensuring that the process is resumed on detach.

In issignal(), when acting on STOPing signals, remove the signal from
queue before suspending.  Otherwise parallel attach could result in
ptracestop() acting on that STOP as if it was the STOP signal from the
attach.  Then SIGSTOP from attach leaks again.

As a minor refactoring, some bits of the common attach code is moved
to new helper proc_set_traced().

Reported by:	markj
Reviewed by:	jhb, markj
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Differential revision:	https://reviews.freebsd.org/D7256
2016-07-28 08:41:13 +00:00
Stephen J. Kiernan
4ac21b4f09 Prepare for network stack as a module
- Move cr_canseeinpcb to sys/netinet/in_prot.c in order to separate the
   INET and INET6-specific code from the rest of the prot code (It is only
   used by the network stack, so it makes sense for it to live with the
   other network stack code.)
 - Move cr_canseeinpcb prototype from sys/systm.h to netinet/in_systm.h
 - Rename cr_seeotheruids to cr_canseeotheruids and cr_seeothergids to
   cr_canseeothergids, make them non-static, and add prototypes (so they
   can be seen/called by in_prot.c functions.)
 - Remove sw_csum variable from ip6_forward in ip6_forward.c, as it is an
   unused variable.

Reviewed by:	gnn, jtl
Approved by:	sjg (mentor)
Sponsored by:	Juniper Networks, Inc.
Differential Revision:	https://reviews.freebsd.org/D2901
2016-07-27 20:34:09 +00:00
John Baldwin
b9a53e161b Adjust tests in fsync job scheduling loop to reduce indentation. 2016-07-27 19:31:25 +00:00
Ed Maste
18c23dffac ANSIfy kern_proc.c and delete register keyword
Reviewed by:	kib
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D6478
2016-07-27 14:27:08 +00:00
Konstantin Belousov
1822421c0b Remove Giant from settime(), tc_setclock_mtx guards tc_windup() calls,
and there is no other issues with parallel settime().  Remove spl()
vestiges there as well.

Tested by:	pho (as part of the whole patch)
Reviewed by:	jhb (same)
Discussed wit:	bde
Sponsored by:	The FreeBSD Foundation
MFC after:	1 month
Differential revision:	https://reviews.freebsd.org/D7302
2016-07-27 11:54:24 +00:00
Konstantin Belousov
5760b029ee Prevent parallel tc_windup() calls, both parallel top-level calls from
setclock() and from simultaneous top-level and interrupt.  For this,
tc_windup() is protected with a tc_setclock_mtx spinlock, in the try
mode when called from hardclock interrupt.  If spinlock cannot be
obtained without spinning from the interrupt context, this means that
top-level executes tc_windup() on other core and our try may be
avoided.

The boottimebin and boottime variables should be adjusted from
tc_windup().  To be correct, they must be part of the timehands and
read using lockless protocol.  Remove the globals and reimplement the
getboottime(9)/getboottimebin(9) KPI using the timehands read
protocol.

Tested by:	pho (as part of the whole patch)
Reviewed by:	jhb (same)
Discussed wit:	bde
Sponsored by:	The FreeBSD Foundation
MFC after:	1 month
X-Differential revision:	https://reviews.freebsd.org/D7302
2016-07-27 11:49:41 +00:00
Konstantin Belousov
4493f659e5 Fix a bug in r302252.
Change ntpadj_lock to spinlock always, and rename stuff removing
ADJ/adj from the names. ntp_update_second() requires ntp_lock and is
called from the tc_windup(), so ntp_lock must be a spinlock.  Add
missed lock to ntp_update_second().

Tested by:	pho (as part of the whole patch)
Reviewed by:	jhb (same)
Noted by:	bde
Sponsored by:	The FreeBSD Foundation
MFC after:	1 month
X-Differential revision:	https://reviews.freebsd.org/D7302
2016-07-27 11:40:06 +00:00
Konstantin Belousov
21547fc7ca Reduce the resettodr_lock scope to only CLOCK_SETTIME() call.
Tested by:	pho (as part of the whole patch)
Reviewed by:	jhb (same)
Discussed with:	bde
Sponsored by:	The FreeBSD Foundation
MFC after:	1 month
X-Differential revision:	https://reviews.freebsd.org/D7302
2016-07-27 11:34:25 +00:00
Konstantin Belousov
4d29106e55 Style.
Sponsored by:	The FreeBSD Foundation
MFC after:	1 month
X-Differential revision:	https://reviews.freebsd.org/D7302
2016-07-27 11:33:33 +00:00
Konstantin Belousov
a83c016f00 Reduce number of timehands to just two. This is useful because
consumers can now be only one tc_windup() call late.

Use C99 initialization.

Tested by:	pho (as part of the whole patch)
Reviewed by:	jhb (same)
Discussed with:	bde
Sponsored by:	The FreeBSD Foundation
MFC after:	1 month
X-Differential revision:	https://reviews.freebsd.org/D7302
2016-07-27 11:27:52 +00:00
Konstantin Belousov
584b675ed6 Hide the boottime and bootimebin globals, provide the getboottime(9)
and getboottimebin(9) KPI. Change consumers of boottime to use the
KPI.  The variables were renamed to avoid shadowing issues with local
variables of the same name.

Issue is that boottime* should be adjusted from tc_windup(), which
requires them to be members of the timehands structure.  As a
preparation, this commit only introduces the interface.

Some uses of boottime were found doubtful, e.g. NLM uses boottime to
identify the system boot instance.  Arguably the identity should not
change on the leap second adjustment, but the commit is about the
timekeeping code and the consumers were kept bug-to-bug compatible.

Tested by:	pho (as part of the bigger patch)
Reviewed by:	jhb (same)
Discussed with:	bde
Sponsored by:	The FreeBSD Foundation
MFC after:	1 month
X-Differential revision:	https://reviews.freebsd.org/D7302
2016-07-27 11:08:59 +00:00
Stephen J. Kiernan
cc37baea09 Add the NUM_CORE_FILES kernel config option which specifies the limit for the
number of core files allowed by a particular process when using the %I core
file name pattern.

Sanity check at compile time to ensure the value is within the valid range of
0-10.

Reviewed by:	jtl, sjg
Approved by:	sjg (mentor)
Sponsored by:	Juniper Networks, Inc.
Differential Revision:	https://reviews.freebsd.org/D6812
2016-07-27 03:21:02 +00:00
Ed Schouten
f63cd251b2 Add shmatt_t.
It looks like our "struct shmid_ds::shm_nattch" deviates from the
standard in the sense that it is a signed integer, whereas POSIX
requires that it is unsigned, having a special type shmatt_t.

Patch up our native and 32-bit copies to use a new shmatt_t that is an
unsigned integer. As it's unsigned, we can relax the comparisons that
are performed on it. Leave the Linux, iBCS2, etc. copies of the
structure alone.

Reviewed by:	ngie
Differential Revision:	https://reviews.freebsd.org/D6655
2016-07-26 17:23:49 +00:00
Conrad Meyer
af326ace9d devfs: Move most ioctl logic down to vnode layer
Devfs' file layer ioctl is now just a thin shim around the vnode layer.

Reviewed by:	kib
Sponsored by:	EMC / Isilon Storage Division
Differential Revision:	https://reviews.freebsd.org/D7286
2016-07-25 16:28:02 +00:00
Konstantin Belousov
90b581f2cc Implement mtx_trylock_spin(9).
Discussed with:	bde
Reviewed by:	jhb
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D7192
2016-07-23 05:30:55 +00:00
John Baldwin
9c20dc9963 Add more documentation regarding unsafe AIO requests.
The asynchronous I/O changes made previously result in different
behavior out of the box. Previously all AIO requests failed with
ENOSYS / SIGSYS unless aio.ko was explicitly loaded. Now, some AIO
requests complete and others ("unsafe" requests) fail with EOPNOTSUPP.

Reword the introductory paragraph in aio(4) to add a general
description of AIO before describing the vfs.aio.enable_unsafe sysctl.

Remove the ENOSYS error description from aio_fsync(2), aio_read(2),
and aio_write(2) and replace it with a description of EOPNOTSUPP.

Remove the ENOSYS error description from aio_mlock(2).

Log a message to the system log the first time a process requests an
"unsafe" AIO request that fails with EOPNOTSUPP. This is modeled on
the log message used for processes using the legacy pty devices.

Reviewed by:	kib (earlier version)
MFC after:	1 week
Sponsored by:	Chelsio Communications
Differential Revision:	https://reviews.freebsd.org/D7151
2016-07-21 22:49:47 +00:00
Konstantin Belousov
492fe1b774 Hide counted_warning(9) under #ifdef _KERNEL braces, to allow building
subr_prf.c in userspace for libsbuf.

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
2016-07-21 17:59:30 +00:00
Konstantin Belousov
9fe297bbdc Declare aio requests on files from local filesystems safe.
Two notes:
- I allow AIO on reclaimed vnodes, since it is deterministically terminated
  fast.
- devfs mounts are marked as MNT_LOCAL, but device vnodes have type
  VCHR, so the slow device io is not allowed.

Reviewed by:	jhb
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D7273
2016-07-21 17:07:06 +00:00
Konstantin Belousov
9837947b07 Provide counter_warning(9) KPI which allows to issue limited number of
warnings for some kernel events, mostly intended for the use of
obsoleted or otherwise undersired interfaces.

This is an abstracted and race-expelled code from compat pty driver.

Requested and reviewed by:	jhb
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D7270
2016-07-21 16:34:56 +00:00
Conrad Meyer
1005d8aff4 imgact_elf: Rename the segment iterator to match reality
The each_writable_segment routine evaluates segments on a slightly little more
nuanced metric than simply "writable" or not.  Rename the function to more
closely match its behavior (each_dumpable_segment).

Suggested by:	jhb
Sponsored by:	EMC / Isilon Storage Division
2016-07-20 22:51:33 +00:00
Conrad Meyer
f3325003d9 ANSI-fy imgact_elf.c
Sponsored by:	EMC / Isilon Storage Division
2016-07-20 22:46:56 +00:00
Conrad Meyer
07f825e871 Fix DEBUG build on 64-bit arch after r303099
Reported by:	Larry Rosenman <ler at lerctr.org>
2016-07-20 18:11:22 +00:00
Conrad Meyer
c17b0bd2a6 Extend ELF coredump to support more than 65535 segments
The ELF e_phnum field is only 16 bits wide. To support more than 65535 segments
(program headers), Sun's "Linker and Libraries Guide" table 7-7 (or 12-7,
depending on document version) prescribes a special first section header where
sh_info represents the real number of program headers.

Test code to follow, when it is ready.

Reference:	http://docs.oracle.com/cd/E18752_01/pdf/817-1984.pdf

Reviewed by:	emaste, markj
Sponsored by:	EMC / Isilon Storage Division
Differential Revision:	https://reviews.freebsd.org/D7255
2016-07-20 16:59:36 +00:00
Gleb Smirnoff
9f3391243b Redo the r302894: the very new value for a non-scheduled callout is -1.
This was recently added in r290664.

Noticed by:	hselasky
Tested by:	Larry Rosenman <ler lerctr.org>
PR:		210884
2016-07-20 16:48:25 +00:00
Gleb Smirnoff
47e4280922 Revert r303037. It re-introduces the panic with TCP timers.
Agreed by:	rrs, re (gjb)
2016-07-20 16:44:22 +00:00
Randall Stewart
3d84a18803 This reverts out Gleb's changes and adds three small
fixes that I think closes up the races Gleb was
looking for. This is running quite nicely in Netflix and
now no longer causes TCP-tcb leaks.

Differential Revision:	7135
2016-07-19 18:31:19 +00:00
John Baldwin
ccb83afd81 Include process IDs in core dumps.
When threads were added to the kernel, the pr_pid member of the
NT_PRSTATUS note was repurposed to store LWP IDs instead of process
IDs.  However, the process ID was no longer recorded in core dumps.
This change adds a pr_pid field to prpsinfo (NT_PRSINFO).  Rather than
bumping the prpsinfo version number, note parsers can use the note's
payload size to determine if pr_pid is present.

Reviewed by:	kib, emaste (older version)
MFC after:	2 months
Differential Revision:	https://reviews.freebsd.org/D7117
2016-07-18 15:14:23 +00:00
John Baldwin
fc4f075a1a Add PTRACE_VFORK to trace vfork events.
First, PL_FLAG_FORKED events now also set a PL_FLAG_VFORKED flag when
the new child was created via vfork() rather than fork().  Second, a
new PL_FLAG_VFORK_DONE event can now be enabled via the PTRACE_VFORK
event mask.  This new stop is reported after the vfork parent resumes
due to the child calling exit or exec.  Debuggers can use this stop to
reinsert breakpoints in the vfork parent process before it resumes.

Reviewed by:	kib
MFC after:	1 month
Differential Revision:	https://reviews.freebsd.org/D7045
2016-07-18 14:53:55 +00:00
Konstantin Belousov
77d6809483 The assertion re-added in r302614 was triggered when stopping signal
is delivered to vforked child.  Issue is that we avoid stopping such
children in issignal() to not block parents.  But executed AST, which
ignored stops, leaves the child with the signal pending but no AST
pending.

On first exec after vfork(), call signotify() to handle pending
reenabled signals.  Adjust the assert to not check vfork children
until exec.

Reported and tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
2016-07-18 10:53:47 +00:00
Gleb Smirnoff
809a9d1353 Revert the last commit. It must get more review and testing first. 2016-07-18 09:29:08 +00:00
Gleb Smirnoff
ef58c6a7a3 Redo the r302894: the very new value for a non-scheduled callout is -1.
This was recently added in r290664.

Noticed by:	hselasky
PR:		210884
2016-07-18 09:26:06 +00:00
Konstantin Belousov
56d48d6dcb Fix another bug after r302350.
Reported and tested by:	pho
PR:	210884
Sponsored by:	The FreeBSD Foundation
MFC after:	3 days
2016-07-18 04:30:34 +00:00
Konstantin Belousov
86f1146329 Another issue reported on http://seclists.org/oss-sec/2016/q3/68 is
that struct kevent member ident has uintptr_t type, which is silently
truncated to int in the call to fget().  Explicitely check for the
valid range.

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
2016-07-16 13:24:58 +00:00
Konstantin Belousov
f470cca578 In ptrace_vm_entry(), do not call vmspace_free() while owning a vm
object lock.

The vmspace_free() operations might need to lock map, object etc on
last dereference.  Postpone the free until object's inspection is
done.

Reported and tested by:	will
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
2016-07-15 23:26:33 +00:00
John Baldwin
8d570f64aa Add a mask of optional ptrace() events.
ptrace() now stores a mask of optional events in p_ptevents.  Currently
this mask is a single integer, but it can be expanded into an array of
integers in the future.

Two new ptrace requests can be used to manipulate the event mask:
PT_GET_EVENT_MASK fetches the current event mask and PT_SET_EVENT_MASK
sets the current event mask.

The current set of events include:
- PTRACE_EXEC: trace calls to execve().
- PTRACE_SCE: trace system call entries.
- PTRACE_SCX: trace syscam call exits.
- PTRACE_FORK: trace forks and auto-attach to new child processes.
- PTRACE_LWP: trace LWP events.

The S_PT_SCX and S_PT_SCE events in the procfs p_stops flags have
been replaced by PTRACE_SCE and PTRACE_SCX.  PTRACE_FORK replaces
P_FOLLOW_FORK and PTRACE_LWP replaces P2_LWP_EVENTS.

The PT_FOLLOW_FORK and PT_LWP_EVENTS ptrace requests remain for
compatibility but now simply toggle corresponding flags in the
event mask.

While here, document that PT_SYSCALL, PT_TO_SCE, and PT_TO_SCX both
modify the event mask and continue the traced process.

Reviewed by:	kib
MFC after:	1 month
Differential Revision:	https://reviews.freebsd.org/D7044
2016-07-15 15:32:09 +00:00
Gleb Smirnoff
2138e263cb Fix regression introduced by r302350. The change of return value for a
callout that wasn't scheduled at all was unintentional and yielded in
several panics.

PR:		210884
2016-07-15 09:28:32 +00:00
Konstantin Belousov
d7e8cfd63d Do not allow creation of char or block special nodes with VNOVAL dev_t.
As was reported on http://seclists.org/oss-sec/2016/q3/68, tmpfs code
contains assertion that rdev != VNOVAL.  On FreeBSD, there is no other
consequences except triggering the assert.  To be compatible with
systems where device nodes have some significance, reject mknod(2)
call with dev == VNOVAL at the syscall level.

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
2016-07-15 09:23:18 +00:00
John Baldwin
c77547d2f9 Include command line arguments in core dump process info.
Fill in pr_psargs in the NT_PRSINFO ELF core dump note with command
line arguments.

Reviewed by:	kib
Differential Revision:	https://reviews.freebsd.org/D7116
2016-07-14 23:20:05 +00:00
Mark Johnston
0649caae32 Let DDB's buf printer handle NULL pointers in the buf page array.
A buf's b_pages and b_npages fields may be inconsistent after a panic.
For instance, vfs_vmio_invalidate() sets b_npages to zero only after all
pages are unwired and their page array entries are cleared.

MFC after:	1 week
Sponsored by:	EMC / Isilon Storage Division
2016-07-14 18:49:05 +00:00
Eric Badger
fdb6320d45 Add explicit detection of KVM hypervisor
Set vm_guest to a new enum value (VM_GUEST_KVM) when kvm is detected and use
vm_guest in conditionals testing for KVM.

Also, fix a conditional checking if we're running in a VM which caught only
the generic VM case, but not more specific VMs (KVM, VMWare, etc.).  (Spotted
by: vangyzen).

Differential revision:	https://reviews.freebsd.org/D7172
Sponsored by:	Dell Inc.
Approved by:	kib (mentor), vangyzen (mentor)
Reviewed by:	alc
MFC after:	4 weeks
2016-07-13 19:19:18 +00:00
Konstantin Belousov
de56aee0bf Trace timeval parameters to the getitimer(2) and setitimer(2) syscalls.
Reviewed by:	jhb
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D7158
2016-07-13 14:37:58 +00:00
Konstantin Belousov
8f01bee46b Revive the check, disabled in r197963.
Despite the implication (process has pending signals -> the current
thread marked for AST and has TDF_NEEDSIGCHK set) is not true due to
other thread might manipulate its signal blocking mask, it should still
hold for the single-threaded processes.  Enable check for the condition
for single-threaded case, and replicate it from userret() to ast() as
well, where we check that ast indeed has no signal to deliver.

Note that the check is under DIAGNOSTIC, it is not enabled for INVARIANTS
but !DIAGNOSTIC since it imposes too heavy-weight locking for day-to-day
used debugging kernel.

Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
2016-07-12 03:53:15 +00:00
Konstantin Belousov
4f4c35bb38 Add assert to complement r302328.
AST must not execute with TDF_SBDRY or TDF_SEINTR/TDF_SERESTART thread
flags set, which is asserted in userret(). As the consequence, -1 return
from cursig() must not be possible.

Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
2016-07-12 03:52:05 +00:00
Nathan Whitehorn
8c636a11dc Remove assumptions in MI code that the BSP is CPU 0.
MFC after:	2 weeks
2016-07-11 21:25:28 +00:00
Konstantin Belousov
725496ced5 Fix grammar.
Submitted by:	alc
MFC after:	2 weeks
2016-07-11 17:04:22 +00:00
Konstantin Belousov
19efd8a5a8 In vgonel(), postpone setting BO_DEAD until VOP_RECLAIM() is called,
if vnode is VMIO.  For VMIO vnodes, set BO_DEAD in vm_object_terminate().

The vnode_destroy_object(), when calling into vm_object_terminate(),
must be able to flush buffers.  BO_DEAD purpose is to quickly destroy
buffers on write when the underlying vnode is not operable any more
(one example is the devfs node after geom is gone).  Setting BO_DEAD
for reclaiming vnode before object is terminated is premature, and
results in unability to flush buffers with live SU dependencies from
vinvalbuf() in vm_object_terminate().

Reported by:	David Cross <dcrosstech@gmail.com>
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
2016-07-11 14:19:09 +00:00
Robert Watson
5fa69ff015 In process-descriptor close(2) and fstat(2), audit target process
information.  pgkill(2) already audits target process ID.

MFC after:	3 days
Sponsored by:	DARPA, AFRL
2016-07-10 14:17:36 +00:00
Robert Watson
e5ec733909 Do allow auditing of read(2) and write(2) system calls, by assigning
those system calls audit event identifiers AUE_READ and AUE_WRITE.
While auditing file-descriptor I/O is not required by the Common
Criteria, in practice this proves useful for both live and forensic
analysis.

NB: freebsd32 already assigns AUE_READ and AUE_WRITE to read(2) and
write(2).

MFC after:	3 days
Sponsored by:	DARPA, AFRL
2016-07-10 13:42:33 +00:00
Robert Watson
8ec75c0fc3 Audit the file-descriptor number argument for openat(2). Remove a comment
about the desirability of auditing the number, as it was in fact in the
wrong place (in the common path for open(2) and openat(2), and only the
latter accepts a file-descriptor argument).  Where other ABIs support
openat(2), it may be necessary to do additional argument auditing as it is
not performed in kern_openat(9).

MFC after:	3 days
Sponsored by:	DARPA, AFRL
2016-07-10 09:50:21 +00:00
Robert Watson
51d1f69069 Audit file-descriptor arguments to I/O system calls such as
read(2), write(2), dup(2), and mmap(2).  This auditing is not
required by the Common Criteria (and hence was not being
performed), but is valuable in both contemporary live analysis
and forensic use cases.

MFC after:	3 days
Sponsored by:	DARPA, AFRL
2016-07-10 08:04:02 +00:00
Edward Tomasz Napierala
debc480e03 Add new unmount(2) flag, MNT_NONBUSY, to check whether there are
any open vnodes before proceeding. Make autounmound(8) use this flag.
Without it, even an unsuccessfull unmount causes filesystem flush,
which interferes with normal operation.

Reviewed by:	kib@
Approved by:	re (gjb@)
MFC after:	1 month
Differential Revision:	https://reviews.freebsd.org/D7047
2016-07-07 09:03:57 +00:00
Nathan Whitehorn
96c85efb4b Replace a number of conflations of mp_ncpus and mp_maxid with either
mp_maxid or CPU_FOREACH() as appropriate. This fixes a number of places in
the kernel that assumed CPU IDs are dense in [0, mp_ncpus) and would try,
for example, to run tasks on CPUs that did not exist or to allocate too
few buffers on systems with sparse CPU IDs in which there are holes in the
range and mp_maxid > mp_ncpus. Such circumstances generally occur on
systems with SMT, but on which SMT is disabled. This patch restores system
operation at least on POWER8 systems configured in this way.

There are a number of other places in the kernel with potential problems
in these situations, but where sparse CPU IDs are not currently known
to occur, mostly in the ARM machine-dependent code. These will be fixed
in a follow-up commit after the stable/11 branch.

PR:		kern/210106
Reviewed by:	jhb
Approved by:	re (glebius)
2016-07-06 14:09:49 +00:00
Gleb Smirnoff
d153eeee97 The paradigm of a callout is that it has three consequent states:
not scheduled -> scheduled -> running -> not scheduled. The API and the
manual page assume that, some comments in the code assume that, and looks
like some contributors to the code also did. The problem is that this
paradigm isn't true. A callout can be scheduled and running at the same
time, which makes API description ambigouous. In such case callout_stop()
family of functions/macros should return 1 and 0 at the same time, since it
successfully unscheduled future callout but the current one is running.
Before this change we returned 1 in such a case, with an exception that
if running callout was migrating we returned 0, unless CS_MIGRBLOCK was
specified.

With this change, we now return 0 in case if future callout was unscheduled,
but another one is still in action, indicating to API users that resources
are not yet safe to be freed.

However, the sleepqueue code relies on getting 1 return code in that case,
and there already was CS_MIGRBLOCK flag, that covered one of the edge cases.
In the new return path we will also use this flag, to keep sleepqueue safe.

Since the flag CS_MIGRBLOCK doesn't block migration and now isn't limited to
migration edge case, rename it to CS_EXECUTING.

This change fixes panics on a high loaded TCP server.

Reviewed by:	jch, hselasky, rrs, kib
Approved by:	re (gjb)
Differential Revision:	https://reviews.freebsd.org/D7042
2016-07-05 18:47:17 +00:00
Gleb Smirnoff
a0d20ecb94 Compile in the kassert_panic() function with INVARIANT_SUPPORT
option, not INVARIANTS.  The function is required if we want
to load in a module that is compiled with INVARIANTS.

Reviewed by:	jhb
Approved by:	re (gjb)
2016-07-05 18:34:34 +00:00
Mark Johnston
f61d6c5a5b Ensure that spinlock sections are balanced even after a panic.
vpanic() uses spinlock_enter() to disable interrupts before dumping core.
However, when the scheduler is stopped and INVARIANTS is not configured,
thread_lock() does not acquire a spinlock section, while thread_unlock()
releases one. This can result in interrupts staying enabled while the
kernel dumps core, complicating post-mortem analysis of the crash.

Approved by:	re (gjb)
MFC after:	1 week
Sponsored by:	EMC / Isilon Storage Division
2016-07-05 17:59:04 +00:00
Robert Watson
971711fb7c Call audit hooks to capture vnode attributes for three file-descriptor
method implementations: fstat(2), close(2), and poll(2).  This change
synchronises auditing here with similar auditing for VFS-specific system
calls such as stat(2) that audit more complete vnode information.

Sponsored by:	DARPA, AFRL
Approved by:	re (kib)
MFC after:	1 week
2016-07-05 16:37:01 +00:00
Ed Maste
1cbb879df8 add description for debug.elf{32,64}_legacy_coredump sysctl
Approved by:	re (kib)
MFC after:	1 week
Sponsored by:	The FreeBSD Foundation
2016-07-05 14:46:06 +00:00
Konstantin Belousov
46e47c4f8d Provide helper macros to detect 'non-silent SBDRY' state and to
calculate appropriate return value for stops.  Simplify the code by
using them.

Fix typo in sig_suspend_threads().  The thread which sleep must be
aborted is td2. (*)

In issignal(), when handling stopping signal for thread in
TD_SBDRY_INTR state, do not stop, this is wrong and fires assert.
This is yet another place where execution should be forced out of
SBDRY-protected region.  For such case, return -1 from issignal() and
translate it to corresponding error code in sleepq_catch_signals().
Assert that other consumers of cursig() are not affected by the new
return value. (*)

Micro-optimize, mostly VFS and VOP methods, by avoiding calling the
functions when SIGDEFERSTOP_NOP non-change is requested. (**)

Reported and tested by:	pho (*)
Requested by:	bde (**)
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Approved by:	re (gjb)
2016-07-03 18:19:48 +00:00
Konstantin Belousov
d12d6a8476 Remove racy assert. The thread which changes vnode usecount from 0 to 1
does it under the vnode interlock, but the interlock is not owned by the
asserting thread.  As result, we might read increased use counter but also
still see VI_OWEINACT.

In collaboration with: nwhitehorn
Hardware donated by: IBM LTC
Sponsored by:	The FreeBSD Foundation (kib)
Approved by:	re (gjb)
2016-07-03 01:56:48 +00:00
Konstantin Belousov
e18ee4957d When a process knote was attached to the process which is already exiting,
the knote is activated immediately.  If the exit1() later activates
knotes, such knote is attempted to be activated second time.  Detect
the condition by zeroed kn_ptr.p_proc pointer, and avoid excessive
activation.

Before r302235, such knotes were removed from the knlist immediately
upon activation.

Reported by:	truckman
Sponsored by:	The FreeBSD Foundation
Approved by:	re (gjb)
2016-07-01 20:11:28 +00:00
Konstantin Belousov
364c516cff Currently the ntptime code and resettodr() are Giant-locked. In
particular, the Giant is supposed to protect against parallel
ntp_adjtime(2) invocations.  But, for instance, sys_ntp_adjtime() does
copyout(9) under Giant and then examines time_status to return syscall
result.  Since copyout(9) could sleep, the syscall result might be
inconsistent.

Another and more important issue is that if PPS is configured,
hardpps(9) is executed without any protection against the parallel
top-level code invocation. Potentially, this may result in the
inconsistent state of the ntptime state variables, but I cannot say
how serious such distortion is. The non-functional splclock() call in
sys_ntp_adjtime() protected against clock interrupts calling hardpps()
in the pre-SMP era.

Modernize the locking. A mutex protects ntptime data.  Due to the
hardpps() KPI legitimately serving from the interrupt filters (and
e.g. uart(4) does call it from filter), the lock cannot be sleepable
mutex if PPS_SYNC is defined.  Otherwise, use normal sleepable mutex
to reduce interrupt latency.

Reviewed by:	  imp, jhb
Sponsored by:	  The FreeBSD Foundation
Approved by:	  re (gjb)
Differential revision:	https://reviews.freebsd.org/D6825
2016-06-28 16:43:23 +00:00
Konstantin Belousov
3a0e6f920a Do not use Giant to prevent parallel calls to CLOCK_SETTIME(). Use
private mtx in resettodr(), no implementation of CLOCK_SETTIME() is
allowed to sleep.

Reviewed by:	  imp, jhb
Sponsored by:	  The FreeBSD Foundation
Approved by:	  re (gjb)
X-Differential revision:	https://reviews.freebsd.org/D6825
2016-06-28 16:42:40 +00:00
Konstantin Belousov
6f56cb8dbf Complete r302215. TDF_SBDRY | TDF_SERESTART and TDF_SBDRY |
TDF_SEINTR flags values, unlike TDF_SBDRY, must be treated almost as
if TDF_SBDRY is not set for STOP signal delivery.  The only difference
is that sig_suspend_threads() should abort the sleep instead of doing
immediate suspension.

Reported by:	ngie
Sponsored by:	The FreeBSD Foundation
MFC after:	12 days
Approved by:	re (gjb)
2016-06-28 16:41:50 +00:00
Konstantin Belousov
9eb3f14324 Fix userspace build after r302235: do not expose bool field of the
structure, change it to int.

The real fix is to sanitize user-visible definitions in sys/event.h,
e.g. the affected struct knlist is of no use for userspace programs.

Reported and tested by:	jkim
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Approved by:	re (gjb)
2016-06-27 23:34:53 +00:00
Konstantin Belousov
9e590ff04b When filt_proc() removes event from the knlist due to the process
exiting (NOTE_EXIT->knlist_remove_inevent()), two things happen:
- knote kn_knlist pointer is reset
- INFLUX knote is removed from the process knlist.
And, there are two consequences:
- KN_LIST_UNLOCK() on such knote is nop
- there is nothing which would block exit1() from processing past the
  knlist_destroy() (and knlist_destroy() resets knlist lock pointers).
Both consequences result either in leaked process lock, or
dereferencing NULL function pointers for locking.

Handle this by stopping embedding the process knlist into struct proc.
Instead, the knlist is allocated together with struct proc, but marked
as autodestroy on the zombie reap, by knlist_detach() function.  The
knlist is freed when last kevent is removed from the list, in
particular, at the zombie reap time if the list is empty.  As result,
the knlist_remove_inevent() is no longer needed and removed.

Other changes:

In filt_procattach(), clear NOTE_EXEC and NOTE_FORK desired events
from kn_sfflags for knote registered by kernel to only get NOTE_CHILD
notifications.  The flags leak resulted in excessive
NOTE_EXEC/NOTE_FORK reports.

Fix immediate note activation in filt_procattach().  Condition should
be either the immediate CHILD_NOTE activation, or immediate NOTE_EXIT
report for the exiting process.

In knote_fork(), do not perform racy check for KN_INFLUX before kq
lock is taken.  Besides being racy, it did not accounted for notes
just added by scan (KN_SCAN).

Some minor and incomplete style fixes.

Analyzed and tested by:	Eric Badger <eric@badgerio.us>
Reviewed by:	jhb
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Approved by:	re (gjb)
Differential revision:	https://reviews.freebsd.org/D6859
2016-06-27 21:52:17 +00:00
Konstantin Belousov
883a5a4a6a When sleeping waiting for either local or remote advisory lock,
interrupt sleeps with the ERESTART on the suspension attempts.
Otherwise, single-threading requests are deferred until the locks are
granted for NFS files, which causes hangs.

When retrying local registration of the remotely-granted adv lock,
allow full suspension and check for suspension, for usual reasons.

Reported by:	markj, pho
Reviewed by:	jilles
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Approved by:	re (gjb)
2016-06-26 20:08:42 +00:00
Konstantin Belousov
3a1e5dd8e6 Rewrite sigdeferstop(9) and sigallowstop(9) into more flexible
framework allowing to set the suspension policy for the dynamic block.
Extend the currently possible policies of stopping on interruptible
sleeps and ignoring such sleeps by two more: do not suspend at
interruptible sleeps, but interrupt them with either EINTR or ERESTART.

Reviewed by:	jilles
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Approved by:	re (gjb)
2016-06-26 20:07:24 +00:00
Konstantin Belousov
8a06de9e92 Do not clear robust lists pointers on fork. The forked child thread
lists must be functional.

Reported by:	Daniel Engberg <daniel.engberg.lists@pyret.net>,
	Guy Yur <guyyur@gmail.com>
Tested by:	Guy Yur <guyyur@gmail.com>
Sponsored by:	The FreeBSD Foundation
Approved by:	re (gjb), including the KBI change
2016-06-25 11:31:25 +00:00
Jilles Tjoelker
6ea906eec0 posixshm: Fix lock leak when mac_posixshm_check_read rejects read.
While reading the code, I noticed that shm_read() returns without unlocking
foffset and rangelock if mac_posixshm_check_read() rejects the read.

Reviewed by:	kib, jhb, rwatson
Approved by:	re (gjb)
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D6927
2016-06-23 20:59:13 +00:00
Brooks Davis
a72c64b0b6 Generate syscall tables and update pipe() implementation after r302094.
Mark the pipe() system call as COMPAT10.

As of r302092 libc uses pipe2() with a zero flags value instead of pipe().

Approved by:	re (gjb)
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D6816
2016-06-22 21:18:19 +00:00
Brooks Davis
e16e64098c Mark the pipe() system call as COMPAT10.
As of r302092 libc uses pipe2() with a zero flags value instead of pipe().

Commit with regenerated files and implementation to follow.

Approved by:	re (gjb)
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D6816
2016-06-22 21:15:59 +00:00
Brooks Davis
e52e02ba24 Add support for COMPAT10 keywords in syscalls.master.
Approved by:	re (gjb)
Sponsored by:	DARPA, AFRL
2016-06-22 21:12:53 +00:00
John Baldwin
b1012d8036 Account for AIO socket operations in thread/process resource usage.
File and disk-backed I/O requests store counts of read/written disk
blocks in each AIO job so that they can be charged to the thread that
completes an AIO request via aio_return() or aio_waitcomplete().  This
change extends AIO jobs to store counts of received/sent messages and
updates socket backends to set these counts accordingly.  Note that
the socket backends are careful to only charge a single messages for
each AIO request even though a single request on a blocking socket might
invoke sosend or soreceive multiple times.  This is to mimic the
resource accounting of synchronous read/write.

Adjust the UNIX socketpair AIO test to verify that the message resource
usage counts update accordingly for aio_read and aio_write.

Approved by:	re (hrs)
Sponsored by:	Chelsio Communications
Differential Revision:	https://reviews.freebsd.org/D6911
2016-06-21 22:19:06 +00:00
Bjoern A. Zeeb
89856f7e2d Get closer to a VIMAGE network stack teardown from top to bottom rather
than removing the network interfaces first. This change is rather larger
and convoluted as the ordering requirements cannot be separated.

Move the pfil(9) framework to SI_SUB_PROTO_PFIL, move Firewalls and
related modules to their own SI_SUB_PROTO_FIREWALL.
Move initialization of "physical" interfaces to SI_SUB_DRIVERS,
move virtual (cloned) interfaces to SI_SUB_PSEUDO.
Move Multicast to SI_SUB_PROTO_MC.

Re-work parts of multicast initialisation and teardown, not taking the
huge amount of memory into account if used as a module yet.

For interface teardown we try to do as many of them as we can on
SI_SUB_INIT_IF, but for some this makes no sense, e.g., when tunnelling
over a higher layer protocol such as IP. In that case the interface
has to go along (or before) the higher layer protocol is shutdown.

Kernel hhooks need to go last on teardown as they may be used at various
higher layers and we cannot remove them before we cleaned up the higher
layers.

For interface teardown there are multiple paths:
(a) a cloned interface is destroyed (inside a VIMAGE or in the base system),
(b) any interface is moved from a virtual network stack to a different
network stack ("vmove"), or (c) a virtual network stack is being shut down.
All code paths go through if_detach_internal() where we, depending on the
vmove flag or the vnet state, make a decision on how much to shut down;
in case we are destroying a VNET the individual protocol layers will
cleanup their own parts thus we cannot do so again for each interface as
we end up with, e.g., double-frees, destroying locks twice or acquiring
already destroyed locks.
When calling into protocol cleanups we equally have to tell them
whether they need to detach upper layer protocols ("ulp") or not
(e.g., in6_ifdetach()).

Provide or enahnce helper functions to do proper cleanup at a protocol
rather than at an interface level.

Approved by:		re (hrs)
Obtained from:		projects/vnet
Reviewed by:		gnn, jhb
Sponsored by:		The FreeBSD Foundation
MFC after:		2 weeks
Differential Revision:	https://reviews.freebsd.org/D6747
2016-06-21 13:48:49 +00:00
Konstantin Belousov
d9a503bec4 Fix typo. Note that atomic is still required even for interlocked case.
Sponsored by:	The FreeBSD Foundation
Approved by:	re (marius)
2016-06-20 15:45:50 +00:00
Mateusz Guzik
e896fb3bae vfs: ifdef out noop vop_* primitives on !DEBUG_VFS_LOCKS kernels
This removes calls to empty functions like vop_lock_{pre/post} from
common vfs routines.

Approved by:	re (gjb)
2016-06-17 19:41:30 +00:00
Konstantin Belousov
f8a75278dc Add VFS interface to flush specified amount of free vnodes belonging
to mount points with the given filesystem type, specified by mount
vfs_ops pointer.

Based on patch by:	mckusick
Reviewed by:	avg, mckusick
Tested by:	allanjude, madpilot
Sponsored by:	The FreeBSD Foundation
Approved by:	re (gjb)
2016-06-17 17:33:25 +00:00
Konstantin Belousov
5c2cf81845 Update comments for the MD functions managing contexts for new
threads, to make it less confusing and using modern kernel terms.

Rename the functions to reflect current use of the functions, instead
of the historic KSE conventions:
  cpu_set_fork_handler -> cpu_fork_kthread_handler (for kthreads)
  cpu_set_upcall -> cpu_copy_thread (for forks)
  cpu_set_upcall_kse -> cpu_set_upcall (for new threads creation)

Reviewed by:	jhb (previous version)
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Approved by:	re (hrs)
Differential revision:	https://reviews.freebsd.org/D6731
2016-06-16 12:05:44 +00:00
Konstantin Belousov
bd07998e0e Remove XXX comments from kern_thread.c. In one case, there is no
reason for it in modern times.  In the other case, expand the comment
stating instead of doubting.

Reviewed by:	jhb
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Approved by:	re (hrs)
X-Differential revision:	https://reviews.freebsd.org/D6731
2016-06-16 12:01:11 +00:00
Konstantin Belousov
13d2cd3b68 Remove code duplication.
Reviewed by:	jhb
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Approved by:	re (hrs)
X-Differential revision:	https://reviews.freebsd.org/D6731
2016-06-16 11:58:46 +00:00
John Baldwin
fe0bdd1d2c Move backend-specific fields of kaiocb into a union.
This reduces the size of kaiocb slightly. I've also added some generic
fields that other backends can use in place of the BIO-specific fields.

Change the socket and Chelsio DDP backends to use 'backend3' instead of
abusing _aiocb_private.status directly. This confines the use of
_aiocb_private to the AIO internals in vfs_aio.c.

Reviewed by:	kib (earlier version)
Approved by:	re (gjb)
Sponsored by:	Chelsio Communications
Differential Revision:	https://reviews.freebsd.org/D6547
2016-06-15 20:56:45 +00:00
Konstantin Belousov
9fdbfd3b6c Do not assume that we own the use reference on the covered vnode until
we set MNTK_UNMOUNT flag on the mp.  Otherwise parallel unmount which
wins race with us could dereference the covered vnode, and we are
left with the locked freed memory.

Reported and tested by:	pho
Sponsored by:	The FreeBSD Foundation
Approved by:	re (gjb)
MFC after:	1 week
2016-06-15 15:56:03 +00:00
Jamie Gritton
932a6e432d Fix a vnode leak when giving a child jail a too-long path when
debug.disablefullpath=1.
2016-06-09 21:59:11 +00:00
Jamie Gritton
cf0313c679 Re-order some jail parameter reading to prevent a vnode leak. 2016-06-09 20:43:14 +00:00
Jamie Gritton
176ff3a066 Clean up some logic in jail error messages, replacing a missing test and
a redundant test with a single correct test.
2016-06-09 20:39:57 +00:00
Mariusz Zaborski
fb4cdc96a8 Define tunable instead of using CTLFLAG_RWTUN flag with kern.corefile.
The allproc_lock lock used in the sysctl_kern_corefile function is initialized
in the procinit function which is called after setting sysctl values at boot.
That means if we set kern.corefile at boot we will be trying to use
lock with is uninitialized and machine will crash.

If we define kern.corefile as tunable instead of using CTFLAG_RWTUN we will
not call the sysctl_kern_corefile function and we will not use an uninitialized
lock. When machine will boot then we will start using function depending on
the lock.

Reviewed by:	pjd
2016-06-09 20:23:30 +00:00
Conrad Meyer
8a3aeac27b Add DDB command "kldstat"
It prints much the same information as kldstat(8) without any arguments.

Suggested by:	jhibbits
Sponsored by:	EMC / Isilon Storage Division
2016-06-09 18:27:41 +00:00
Conrad Meyer
dd6ea7f7bc kvprintf: Pad %*c to width, like %*s
Sponsored by:	EMC / Isilon Storage Division
2016-06-09 18:24:51 +00:00
Jamie Gritton
ef0ddea316 Make sure the OSD methods for jail set and remove can't run concurrently,
by holding allprison_lock exclusively (even if only for a moment before
downgrading) on all paths that call PR_METHOD_REMOVE.  Since they may run
on a downgraded lock, it's still possible for them to run concurrently
with PR_METHOD_GET, which will need to use the prison lock.
2016-06-09 16:41:41 +00:00