mirror of
https://github.com/opnsense/src.git
synced 2026-05-28 04:12:45 -04:00
linux(4): Implement pi futexes using umtx.
Differential Revision: https://reviews.freebsd.org/D31240 MFC after: 2 weeks
This commit is contained in:
Dmitry Chagin
parent
cb01cc4a10
commit
7a718f293a
2 changed files with 326 additions and 30 deletions
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@ -45,6 +45,7 @@ __FBSDID("$FreeBSD$");
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#include <sys/sched.h>
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#include <sys/syscallsubr.h>
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#include <sys/sx.h>
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#include <sys/umtxvar.h>
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#include <sys/unistd.h>
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#include <sys/wait.h>
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@ -436,4 +437,10 @@ linux_thread_detach(struct thread *td)
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if (error != 0)
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linux_msg(td, "futex stuff in thread_detach failed.");
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}
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/*
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* Do not rely on the robust list which is maintained by userspace,
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* cleanup remaining pi (if any) after release_futexes anyway.
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*/
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umtx_thread_exit(td);
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}
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@ -71,6 +71,7 @@ __KERNEL_RCSID(1, "$NetBSD: linux_futex.c,v 1.7 2006/07/24 19:01:49 manu Exp $")
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#include <compat/linux/linux_dtrace.h>
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#include <compat/linux/linux_emul.h>
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#include <compat/linux/linux_futex.h>
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#include <compat/linux/linux_misc.h>
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#include <compat/linux/linux_timer.h>
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#include <compat/linux/linux_util.h>
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@ -92,9 +93,6 @@ LIN_SDT_PROBE_DEFINE5(futex, linux_futex, debug_cmp_requeue, "uint32_t *",
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"uint32_t", "uint32_t", "uint32_t *", "struct l_timespec *");
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LIN_SDT_PROBE_DEFINE5(futex, linux_futex, debug_wake_op, "uint32_t *",
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"int", "uint32_t", "uint32_t *", "uint32_t");
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LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unimplemented_lock_pi);
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LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unimplemented_unlock_pi);
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LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unimplemented_trylock_pi);
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LIN_SDT_PROBE_DEFINE0(futex, linux_futex, deprecated_requeue);
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LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unimplemented_wait_requeue_pi);
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LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unimplemented_cmp_requeue_pi);
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@ -134,6 +132,10 @@ static int linux_futex_wait(struct thread *, struct linux_futex_args *);
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static int linux_futex_wake(struct thread *, struct linux_futex_args *);
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static int linux_futex_requeue(struct thread *, struct linux_futex_args *);
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static int linux_futex_wakeop(struct thread *, struct linux_futex_args *);
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static int linux_futex_lock_pi(struct thread *, bool, struct linux_futex_args *);
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static int linux_futex_unlock_pi(struct thread *, bool,
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struct linux_futex_args *);
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static int futex_wake_pi(struct thread *, uint32_t *, bool);
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int
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futex_wake(struct thread *td, uint32_t *uaddr, int val, bool shared)
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@ -150,6 +152,19 @@ futex_wake(struct thread *td, uint32_t *uaddr, int val, bool shared)
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return (linux_futex_wake(td, &args));
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}
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static int
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futex_wake_pi(struct thread *td, uint32_t *uaddr, bool shared)
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{
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struct linux_futex_args args;
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bzero(&args, sizeof(args));
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args.op = LINUX_FUTEX_UNLOCK_PI;
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args.uaddr = uaddr;
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args.flags = shared == true ? FUTEX_SHARED : 0;
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return (linux_futex_unlock_pi(td, true, &args));
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}
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static int
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futex_atomic_op(struct thread *td, int encoded_op, uint32_t *uaddr)
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{
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@ -306,37 +321,23 @@ linux_futex(struct thread *td, struct linux_futex_args *args)
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return (linux_futex_wakeop(td, args));
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case LINUX_FUTEX_LOCK_PI:
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/* not yet implemented */
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pem = pem_find(td->td_proc);
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if ((pem->flags & LINUX_XUNSUP_FUTEXPIOP) == 0) {
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linux_msg(td, "unsupported FUTEX_LOCK_PI");
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pem->flags |= LINUX_XUNSUP_FUTEXPIOP;
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LIN_SDT_PROBE0(futex, linux_futex,
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unimplemented_lock_pi);
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}
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return (ENOSYS);
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args->clockrt = true;
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LINUX_CTR2(sys_futex, "LOCKPI uaddr %p val 0x%x",
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args->uaddr, args->val);
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return (linux_futex_lock_pi(td, false, args));
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case LINUX_FUTEX_UNLOCK_PI:
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/* not yet implemented */
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pem = pem_find(td->td_proc);
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if ((pem->flags & LINUX_XUNSUP_FUTEXPIOP) == 0) {
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linux_msg(td, "unsupported FUTEX_UNLOCK_PI");
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pem->flags |= LINUX_XUNSUP_FUTEXPIOP;
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LIN_SDT_PROBE0(futex, linux_futex,
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unimplemented_unlock_pi);
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}
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return (ENOSYS);
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LINUX_CTR1(sys_futex, "UNLOCKPI uaddr %p",
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args->uaddr);
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return (linux_futex_unlock_pi(td, false, args));
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case LINUX_FUTEX_TRYLOCK_PI:
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/* not yet implemented */
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pem = pem_find(td->td_proc);
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if ((pem->flags & LINUX_XUNSUP_FUTEXPIOP) == 0) {
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linux_msg(td, "unsupported FUTEX_TRYLOCK_PI");
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pem->flags |= LINUX_XUNSUP_FUTEXPIOP;
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LIN_SDT_PROBE0(futex, linux_futex,
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unimplemented_trylock_pi);
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}
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return (ENOSYS);
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LINUX_CTR1(sys_futex, "TRYLOCKPI uaddr %p",
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args->uaddr);
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return (linux_futex_lock_pi(td, true, args));
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case LINUX_FUTEX_WAIT_REQUEUE_PI:
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/* not yet implemented */
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@ -368,6 +369,288 @@ linux_futex(struct thread *td, struct linux_futex_args *args)
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}
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}
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/*
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* pi protocol:
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* - 0 futex word value means unlocked.
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* - TID futex word value means locked.
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* Userspace uses atomic ops to lock/unlock these futexes without entering the
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* kernel. If the lock-acquire fastpath fails, (transition from 0 to TID fails),
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* then FUTEX_LOCK_PI is called.
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* The kernel atomically set FUTEX_WAITERS bit in the futex word value, if no
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* other waiters exists looks up the thread that owns the futex (it has put its
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* own TID into the futex value) and made this thread the owner of the internal
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* pi-aware lock object (mutex). Then the kernel tries to lock the internal lock
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* object, on which it blocks. Once it returns, it has the mutex acquired, and it
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* sets the futex value to its own TID and returns (futex value contains
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* FUTEX_WAITERS|TID).
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* The unlock fastpath would fail (because the FUTEX_WAITERS bit is set) and
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* FUTEX_UNLOCK_PI will be called.
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* If a futex is found to be held at exit time, the kernel sets the OWNER_DIED
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* bit of the futex word and wakes up the next futex waiter (if any), WAITERS
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* bit is preserved (if any).
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* If OWNER_DIED bit is set the kernel sanity checks the futex word value against
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* the internal futex state and if correct, acquire futex.
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*/
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static int
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linux_futex_lock_pi(struct thread *td, bool try, struct linux_futex_args *args)
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{
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struct umtx_abs_timeout timo;
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struct linux_emuldata *em;
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struct umtx_pi *pi, *new_pi;
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struct thread *td1;
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struct umtx_q *uq;
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int error, rv;
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uint32_t owner, old_owner;
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em = em_find(td);
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uq = td->td_umtxq;
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error = umtx_key_get(args->uaddr, TYPE_PI_FUTEX, GET_SHARED(args),
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&uq->uq_key);
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if (error != 0)
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return (error);
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if (args->ts != NULL)
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linux_umtx_abs_timeout_init(&timo, args);
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umtxq_lock(&uq->uq_key);
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pi = umtx_pi_lookup(&uq->uq_key);
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if (pi == NULL) {
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new_pi = umtx_pi_alloc(M_NOWAIT);
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if (new_pi == NULL) {
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umtxq_unlock(&uq->uq_key);
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new_pi = umtx_pi_alloc(M_WAITOK);
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umtxq_lock(&uq->uq_key);
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pi = umtx_pi_lookup(&uq->uq_key);
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if (pi != NULL) {
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umtx_pi_free(new_pi);
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new_pi = NULL;
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}
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}
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if (new_pi != NULL) {
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new_pi->pi_key = uq->uq_key;
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umtx_pi_insert(new_pi);
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pi = new_pi;
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}
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}
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umtx_pi_ref(pi);
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umtxq_unlock(&uq->uq_key);
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for (;;) {
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/* Try uncontested case first. */
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rv = casueword32(args->uaddr, 0, &owner, em->em_tid);
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/* The acquire succeeded. */
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if (rv == 0) {
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error = 0;
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break;
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}
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if (rv == -1) {
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error = EFAULT;
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break;
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}
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/*
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* Avoid overwriting a possible error from sleep due
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* to the pending signal with suspension check result.
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*/
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if (error == 0) {
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error = thread_check_susp(td, true);
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if (error != 0)
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break;
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}
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/* The futex word at *uaddr is already locked by the caller. */
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if ((owner & FUTEX_TID_MASK) == em->em_tid) {
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error = EDEADLK;
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break;
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}
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/*
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* Futex owner died, handle_futex_death() set the OWNER_DIED bit
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* and clear tid. Try to acquire it.
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*/
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if ((owner & FUTEX_TID_MASK) == 0) {
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old_owner = owner;
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owner = owner & (FUTEX_WAITERS | FUTEX_OWNER_DIED);
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owner |= em->em_tid;
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rv = casueword32(args->uaddr, old_owner, &owner, owner);
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if (rv == -1) {
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error = EFAULT;
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break;
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}
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if (rv == 1) {
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if (error == 0) {
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error = thread_check_susp(td, true);
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if (error != 0)
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break;
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}
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/*
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* If this failed the lock could
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* changed, restart.
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*/
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continue;
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}
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umtxq_lock(&uq->uq_key);
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umtxq_busy(&uq->uq_key);
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error = umtx_pi_claim(pi, td);
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umtxq_unbusy(&uq->uq_key);
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umtxq_unlock(&uq->uq_key);
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if (error != 0) {
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/*
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* Since we're going to return an
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* error, restore the futex to its
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* previous, unowned state to avoid
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* compounding the problem.
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*/
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(void)casuword32(args->uaddr, owner, old_owner);
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}
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break;
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}
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/*
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* Inconsistent state: OWNER_DIED is set and tid is not 0.
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* Linux does some checks of futex state, we return EINVAL,
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* as the user space can take care of this.
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*/
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if ((owner & FUTEX_OWNER_DIED) != 0) {
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error = EINVAL;
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break;
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}
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if (try != 0) {
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error = EBUSY;
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break;
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}
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/*
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* If we caught a signal, we have retried and now
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* exit immediately.
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*/
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if (error != 0)
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break;
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umtxq_lock(&uq->uq_key);
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umtxq_busy(&uq->uq_key);
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umtxq_unlock(&uq->uq_key);
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/*
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* Set the contested bit so that a release in user space knows
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* to use the system call for unlock. If this fails either some
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* one else has acquired the lock or it has been released.
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*/
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rv = casueword32(args->uaddr, owner, &owner,
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owner | FUTEX_WAITERS);
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if (rv == -1) {
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umtxq_unbusy_unlocked(&uq->uq_key);
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error = EFAULT;
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break;
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}
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if (rv == 1) {
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umtxq_unbusy_unlocked(&uq->uq_key);
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error = thread_check_susp(td, true);
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if (error != 0)
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break;
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/*
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* The lock changed and we need to retry or we
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* lost a race to the thread unlocking the umtx.
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*/
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continue;
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}
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/*
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* Substitute Linux thread id by native thread id to
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* avoid refactoring code of umtxq_sleep_pi().
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*/
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td1 = linux_tdfind(td, owner & FUTEX_TID_MASK, -1);
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if (td1 != NULL) {
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owner = td1->td_tid;
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PROC_UNLOCK(td1->td_proc);
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} else {
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umtxq_unbusy_unlocked(&uq->uq_key);
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error = EINVAL;
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break;
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}
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umtxq_lock(&uq->uq_key);
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/* We set the contested bit, sleep. */
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error = umtxq_sleep_pi(uq, pi, owner, "futexp",
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args->ts == NULL ? NULL : &timo,
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(args->flags & FUTEX_SHARED) != 0);
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if (error != 0)
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continue;
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error = thread_check_susp(td, false);
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if (error != 0)
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break;
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}
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umtxq_lock(&uq->uq_key);
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umtx_pi_unref(pi);
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umtxq_unlock(&uq->uq_key);
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umtx_key_release(&uq->uq_key);
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return (error);
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}
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static int
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linux_futex_unlock_pi(struct thread *td, bool rb, struct linux_futex_args *args)
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{
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struct linux_emuldata *em;
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struct umtx_key key;
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uint32_t old, owner, new_owner;
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int count, error;
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em = em_find(td);
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/*
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* Make sure we own this mtx.
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*/
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error = fueword32(args->uaddr, &owner);
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if (error == -1)
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return (EFAULT);
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if (!rb && (owner & FUTEX_TID_MASK) != em->em_tid)
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return (EPERM);
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error = umtx_key_get(args->uaddr, TYPE_PI_FUTEX, GET_SHARED(args), &key);
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if (error != 0)
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return (error);
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umtxq_lock(&key);
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umtxq_busy(&key);
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error = umtx_pi_drop(td, &key, rb, &count);
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if (error != 0 || rb) {
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umtxq_unbusy(&key);
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umtxq_unlock(&key);
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umtx_key_release(&key);
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return (error);
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}
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umtxq_unlock(&key);
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/*
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* When unlocking the futex, it must be marked as unowned if
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* there is zero or one thread only waiting for it.
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* Otherwise, it must be marked as contested.
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*/
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if (count > 1)
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new_owner = FUTEX_WAITERS;
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else
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new_owner = 0;
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again:
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error = casueword32(args->uaddr, owner, &old, new_owner);
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if (error == 1) {
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error = thread_check_susp(td, false);
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if (error == 0)
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goto again;
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}
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umtxq_unbusy_unlocked(&key);
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umtx_key_release(&key);
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if (error == -1)
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return (EFAULT);
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if (error == 0 && old != owner)
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return (EINVAL);
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return (error);
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}
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static int
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linux_futex_wakeop(struct thread *td, struct linux_futex_args *args)
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{
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@ -576,6 +859,7 @@ linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
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switch (args->op & LINUX_FUTEX_CMD_MASK) {
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case LINUX_FUTEX_WAIT:
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case LINUX_FUTEX_WAIT_BITSET:
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case LINUX_FUTEX_LOCK_PI:
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if (args->timeout != NULL) {
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error = copyin(args->timeout, <s, sizeof(lts));
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if (error != 0)
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@ -611,6 +895,7 @@ linux_sys_futex_time64(struct thread *td,
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switch (args->op & LINUX_FUTEX_CMD_MASK) {
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case LINUX_FUTEX_WAIT:
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case LINUX_FUTEX_WAIT_BITSET:
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case LINUX_FUTEX_LOCK_PI:
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if (args->timeout != NULL) {
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error = copyin(args->timeout, <s, sizeof(lts));
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if (error != 0)
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@ -721,6 +1006,10 @@ retry:
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error = futex_wake(curthread, uaddr, 1, true);
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if (error != 0)
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return (error);
|
||||
} else if (pi && (uval & FUTEX_WAITERS)) {
|
||||
error = futex_wake_pi(curthread, uaddr, true);
|
||||
if (error != 0)
|
||||
return (error);
|
||||
}
|
||||
}
|
||||
|
||||
|
|
|
|||
Loading…
Reference in a new issue