Use umtx_key objects to uniquely identify futexes. Private futexes in
different processes that happen to use the same user address in the separate processes will now be treated as distinct futexes rather than the same futex. We can now honor shared futexes properly by mapping them to a PROCESS_SHARED umtx_key. Private futexes use THREAD_SHARED umtx_key objects. In conjunction with: dchagin Reviewed by: kib MFC after: 1 week
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jhb
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@ -52,6 +52,7 @@ __KERNEL_RCSID(1, "$NetBSD: linux_futex.c,v 1.7 2006/07/24 19:01:49 manu Exp $")
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#include <sys/queue.h>
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#include <sys/sched.h>
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#include <sys/sx.h>
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#include <sys/umtx.h>
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#ifdef COMPAT_LINUX32
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#include <machine/../linux32/linux.h>
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@ -77,7 +78,8 @@ struct waiting_proc {
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struct futex {
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struct sx f_lck;
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uint32_t *f_uaddr;
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uint32_t *f_uaddr; /* user-supplied value, for debug */
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struct umtx_key f_key;
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uint32_t f_refcount;
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uint32_t f_bitset;
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LIST_ENTRY(futex) f_list;
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@ -100,6 +102,7 @@ struct mtx futex_mtx; /* protects the futex list */
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#define FUTEX_CREATE_WP 0x1 /* create waiting_proc */
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#define FUTEX_DONTCREATE 0x2 /* don't create futex if not exists */
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#define FUTEX_DONTEXISTS 0x4 /* return EINVAL if futex exists */
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#define FUTEX_SHARED 0x8 /* shared futex */
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/* wp_flags */
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#define FUTEX_WP_REQUEUED 0x1 /* wp requeued - wp moved from wp_list
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@ -136,6 +139,7 @@ futex_put(struct futex *f, struct waiting_proc *wp)
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LINUX_CTR2(sys_futex, "futex_put destroy uaddr %p ref %d",
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f->f_uaddr, f->f_refcount);
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umtx_key_release(&f->f_key);
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FUTEX_DESTROY(f);
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free(f, M_FUTEX);
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return;
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@ -151,13 +155,19 @@ static int
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futex_get0(uint32_t *uaddr, struct futex **newf, uint32_t flags)
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{
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struct futex *f, *tmpf;
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struct umtx_key key;
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int error;
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*newf = tmpf = NULL;
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error = umtx_key_get(uaddr, TYPE_FUTEX, (flags & FUTEX_SHARED) ?
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PROCESS_SHARE : THREAD_SHARE, &key);
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if (error)
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return (error);
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retry:
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FUTEXES_LOCK;
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LIST_FOREACH(f, &futex_list, f_list) {
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if (f->f_uaddr == uaddr) {
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if (umtx_key_match(&f->f_key, &key)) {
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if (tmpf != NULL) {
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FUTEX_UNLOCK(tmpf);
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FUTEX_DESTROY(tmpf);
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@ -165,6 +175,7 @@ retry:
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}
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if (flags & FUTEX_DONTEXISTS) {
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FUTEXES_UNLOCK;
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umtx_key_release(&key);
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return (EINVAL);
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}
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@ -174,6 +185,7 @@ retry:
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*/
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++f->f_refcount;
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FUTEXES_UNLOCK;
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umtx_key_release(&key);
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FUTEX_LOCK(f);
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*newf = f;
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@ -185,6 +197,7 @@ retry:
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if (flags & FUTEX_DONTCREATE) {
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FUTEXES_UNLOCK;
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umtx_key_release(&key);
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LINUX_CTR1(sys_futex, "futex_get uaddr %p null", uaddr);
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return (0);
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}
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@ -193,6 +206,7 @@ retry:
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FUTEXES_UNLOCK;
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tmpf = malloc(sizeof(*tmpf), M_FUTEX, M_WAITOK | M_ZERO);
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tmpf->f_uaddr = uaddr;
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tmpf->f_key = key;
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tmpf->f_refcount = 1;
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tmpf->f_bitset = FUTEX_BITSET_MATCH_ANY;
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FUTEX_INIT(tmpf);
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@ -438,15 +452,13 @@ linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
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struct waiting_proc *wp;
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struct futex *f, *f2;
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int error;
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uint32_t flags;
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/*
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* Our implementation provides only privates futexes. Most of the apps
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* should use private futexes but don't claim so. Therefore we treat
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* all futexes as private by clearing the FUTEX_PRIVATE_FLAG. It works
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* in most cases (ie. when futexes are not shared on file descriptor
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* or between different processes.).
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*/
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args->op = args->op & ~LINUX_FUTEX_PRIVATE_FLAG;
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if (args->op & LINUX_FUTEX_PRIVATE_FLAG) {
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flags = 0;
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args->op &= ~LINUX_FUTEX_PRIVATE_FLAG;
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} else
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flags = FUTEX_SHARED;
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/*
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* Currently support for switching between CLOCK_MONOTONIC and
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@ -478,7 +490,8 @@ linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
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"futex_wait uaddr %p val %d val3 %d"),
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args->uaddr, args->val, args->val3);
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#endif
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error = futex_get(args->uaddr, &wp, &f, FUTEX_CREATE_WP);
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error = futex_get(args->uaddr, &wp, &f,
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flags | FUTEX_CREATE_WP);
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if (error)
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return (error);
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error = copyin(args->uaddr, &val, sizeof(val));
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@ -518,7 +531,8 @@ linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
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printf(ARGS(sys_futex, "futex_wake uaddr %p val %d val3 %d"),
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args->uaddr, args->val, args->val3);
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#endif
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error = futex_get(args->uaddr, NULL, &f, FUTEX_DONTCREATE);
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error = futex_get(args->uaddr, NULL, &f,
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flags | FUTEX_DONTCREATE);
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if (error)
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return (error);
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if (f == NULL) {
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@ -550,7 +564,7 @@ linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
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*/
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if (args->uaddr == args->uaddr2)
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return (EINVAL);
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error = futex_get0(args->uaddr, &f, 0);
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error = futex_get(args->uaddr, NULL, &f, flags);
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if (error)
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return (error);
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@ -561,7 +575,8 @@ linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
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* Glibc fall back to FUTEX_WAKE in case of any error
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* returned by FUTEX_CMP_REQUEUE.
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*/
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error = futex_get0(args->uaddr2, &f2, FUTEX_DONTEXISTS);
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error = futex_get(args->uaddr2, NULL, &f2,
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flags | FUTEX_DONTEXISTS);
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if (error) {
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futex_put(f, NULL);
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return (error);
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@ -602,11 +617,11 @@ linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
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args->uaddr, args->op, args->val,
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args->uaddr2, args->val3);
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#endif
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error = futex_get0(args->uaddr, &f, 0);
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error = futex_get(args->uaddr, NULL, &f, flags);
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if (error)
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return (error);
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if (args->uaddr != args->uaddr2)
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error = futex_get0(args->uaddr2, &f2, 0);
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error = futex_get(args->uaddr2, NULL, &f2, flags);
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if (error) {
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futex_put(f, NULL);
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return (error);
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@ -800,7 +815,7 @@ retry:
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if (!pi && (uval & FUTEX_WAITERS)) {
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error = futex_get(uaddr, NULL, &f,
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FUTEX_DONTCREATE);
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FUTEX_DONTCREATE | FUTEX_SHARED);
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if (error)
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return (error);
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if (f != NULL) {
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@ -185,6 +185,7 @@ enum {
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TYPE_PI_UMUTEX,
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TYPE_PP_UMUTEX,
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TYPE_RWLOCK,
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TYPE_FUTEX
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};
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/* Key to represent a unique userland synchronous object */
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