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Revert "dtrace: make 'ring' and 'fill' policies imply 'noswitch' flag"

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This reverts commit e92491d95f.

The general idea looked good to me.  In particular, it allowed to save
some memory and avoid memory allocation failures when a large buffer
size was requested along with ring and fill policies.

But I didn't take into account that the second, supposedly unused
buffer, was actually used as the scratch buffer.  The scratch buffer is
used as a temporary space for DTrace subroutines like copyin, copyinstr,
and alloca.

I think that the change can be fixed by allocating a separate smaller
buffer for the scratch buffer, but that fix would require more work than
I am able to do now.  Hence the revert.

Reported by:	Domagoj Stolfa
Diagnosed by:	Domagoj Stolfa, markj
MFC after:	immediately
This commit is contained in:
Andriy Gapon 2024-04-21 13:07:36 +03:00
parent 26f6c148bc
commit b9827c007a
1 changed files with 3 additions and 2 deletions
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5
sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c
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@ -12058,6 +12058,7 @@ dtrace_buffer_switch(dtrace_buffer_t *buf)
hrtime_t now;
ASSERT(!(buf->dtb_flags & DTRACEBUF_NOSWITCH));
ASSERT(!(buf->dtb_flags & DTRACEBUF_RING));
cookie = dtrace_interrupt_disable();
now = dtrace_gethrtime();
@ -14865,10 +14866,10 @@ dtrace_state_buffer(dtrace_state_t *state, dtrace_buffer_t *buf, int which)
if (which == DTRACEOPT_BUFSIZE) {
if (opt[DTRACEOPT_BUFPOLICY] == DTRACEOPT_BUFPOLICY_RING)
flags |= DTRACEBUF_RING | DTRACEBUF_NOSWITCH;
flags |= DTRACEBUF_RING;
if (opt[DTRACEOPT_BUFPOLICY] == DTRACEOPT_BUFPOLICY_FILL)
flags |= DTRACEBUF_FILL | DTRACEBUF_NOSWITCH;
flags |= DTRACEBUF_FILL;
if (state != dtrace_anon.dta_state ||
state->dts_activity != DTRACE_ACTIVITY_ACTIVE)