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Pull up following revision(s) (requested by riastradh in ticket #1696): 

sys/external/bsd/drm2/linux/linux_ww_mutex.c: revision 1.15

drm/linux_ww_mutex: Fix wait loops.

If cv_wait_sig returns because a signal is delivered, we may
nonetheless have been granted the lock.  It is harmless for us to
ignore this fact in three of the four paths, but in
ww_mutex_state_wait_sig, we may now have ownership of the lock and
MUST NOT return failure because the caller MUST release the lock
before destroying the ww_acquire_ctx.

While here, restructure the other three loops for clarity, so they
match the structure of the fourth and so they have a little less
impenetrable negation.

PR kern/57537
This commit is contained in:
martin 2023-08-01 17:26:28 +00:00
parent c6bf52d6ed
commit af56efbd87
1 changed files with 44 additions and 16 deletions
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60
sys/external/bsd/drm2/linux/linux_ww_mutex.c vendored
View File

@ -1,4 +1,4 @@
/* $NetBSD: linux_ww_mutex.c,v 1.7.2.2 2023/08/01 17:16:26 martin Exp $ */
/* $NetBSD: linux_ww_mutex.c,v 1.7.2.3 2023/08/01 17:26:28 martin Exp $ */
/*-
* Copyright (c) 2014 The NetBSD Foundation, Inc.
@ -30,7 +30,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: linux_ww_mutex.c,v 1.7.2.2 2023/08/01 17:16:26 martin Exp $");
__KERNEL_RCSID(0, "$NetBSD: linux_ww_mutex.c,v 1.7.2.3 2023/08/01 17:26:28 martin Exp $");
#include <sys/types.h>
#include <sys/atomic.h>
@ -271,8 +271,14 @@ ww_mutex_state_wait(struct ww_mutex *mutex, enum ww_mutex_state state)
KASSERT(mutex_owned(&mutex->wwm_lock));
KASSERT(mutex->wwm_state == state);
do cv_wait(&mutex->wwm_cv, &mutex->wwm_lock);
while (mutex->wwm_state == state);
for (;;) {
cv_wait(&mutex->wwm_cv, &mutex->wwm_lock);
if (mutex->wwm_state != state)
break;
}
KASSERT(mutex->wwm_state != state);
}
/*
@ -295,18 +301,26 @@ ww_mutex_state_wait_sig(struct ww_mutex *mutex, enum ww_mutex_state state)
KASSERT(mutex_owned(&mutex->wwm_lock));
KASSERT(mutex->wwm_state == state);
do {
for (;;) {
/* XXX errno NetBSD->Linux */
ret = -cv_wait_sig(&mutex->wwm_cv, &mutex->wwm_lock);
if (mutex->wwm_state != state) {
ret = 0;
break;
}
if (ret) {
KASSERTMSG((ret == -EINTR || ret == -ERESTART),
"ret=%d", ret);
ret = -EINTR;
break;
}
} while (mutex->wwm_state == state);
}
KASSERTMSG((ret == 0 || ret == -EINTR), "ret=%d", ret);
KASSERTMSG(ret != 0 || mutex->wwm_state != state,
"ret=%d mutex=%p mutex->wwm_state=%d state=%d",
ret, mutex, mutex->wwm_state, state);
return ret;
}
@ -348,12 +362,18 @@ ww_mutex_lock_wait(struct ww_mutex *mutex, struct ww_acquire_ctx *ctx)
"ticket number reused: %"PRId64" (%p) %"PRId64" (%p)",
ctx->wwx_ticket, ctx, collision->wwx_ticket, collision);
do cv_wait(&mutex->wwm_cv, &mutex->wwm_lock);
while (!(((mutex->wwm_state == WW_CTX) ||
(mutex->wwm_state == WW_WANTOWN)) &&
(mutex->wwm_u.ctx == ctx)));
for (;;) {
cv_wait(&mutex->wwm_cv, &mutex->wwm_lock);
if ((mutex->wwm_state == WW_CTX ||
mutex->wwm_state == WW_WANTOWN) &&
mutex->wwm_u.ctx == ctx)
break;
}
rb_tree_remove_node(&mutex->wwm_waiters, ctx);
KASSERT(mutex->wwm_state == WW_CTX || mutex->wwm_state == WW_WANTOWN);
KASSERT(mutex->wwm_u.ctx == ctx);
}
/*
@ -396,21 +416,29 @@ ww_mutex_lock_wait_sig(struct ww_mutex *mutex, struct ww_acquire_ctx *ctx)
"ticket number reused: %"PRId64" (%p) %"PRId64" (%p)",
ctx->wwx_ticket, ctx, collision->wwx_ticket, collision);
do {
for (;;) {
/* XXX errno NetBSD->Linux */
ret = -cv_wait_sig(&mutex->wwm_cv, &mutex->wwm_lock);
if ((mutex->wwm_state == WW_CTX ||
mutex->wwm_state == WW_WANTOWN) &&
mutex->wwm_u.ctx == ctx) {
ret = 0;
break;
}
if (ret) {
KASSERTMSG((ret == -EINTR || ret == -ERESTART),
"ret=%d", ret);
ret = -EINTR;
goto out;
break;
}
} while (!(((mutex->wwm_state == WW_CTX) ||
(mutex->wwm_state == WW_WANTOWN)) &&
(mutex->wwm_u.ctx == ctx)));
}
rb_tree_remove_node(&mutex->wwm_waiters, ctx);
out: rb_tree_remove_node(&mutex->wwm_waiters, ctx);
KASSERTMSG((ret == 0 || ret == -EINTR), "ret=%d", ret);
KASSERT(ret != 0 ||
mutex->wwm_state == WW_CTX || mutex->wwm_state == WW_WANTOWN);
KASSERT(ret != 0 || mutex->wwm_u.ctx == ctx);
return ret;
}