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Cache the value of c_lock as it can change, in the struct,

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while the global callout spinlock is not held, and can lead to PF#.

Reported by: dougb, Mark Atkinson <atkin901 at yahoo dot com>
Tested by: dougb
Diagnosed by: jhb
This commit is contained in:
attilio 2007-11-22 12:15:54 +00:00
parent 2b0672aa28
commit 5ed5cf01be
1 changed files with 7 additions and 5 deletions
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12
sys/kern/kern_timeout.c
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@ -216,6 +216,7 @@ softclock(void *dummy)
void (*c_func)(void *);
void *c_arg;
struct lock_class *class;
struct lock_object *c_lock;
int c_flags, sharedlock;
nextsoftcheck = TAILQ_NEXT(c, c_links.tqe);
@ -224,6 +225,7 @@ softclock(void *dummy)
LOCK_CLASS(c->c_lock) : NULL;
sharedlock = (c->c_flags & CALLOUT_SHAREDLOCK) ?
0 : 1;
c_lock = c->c_lock;
c_func = c->c_func;
c_arg = c->c_arg;
c_flags = c->c_flags;
@ -240,20 +242,20 @@ softclock(void *dummy)
}
curr_cancelled = 0;
mtx_unlock_spin(&callout_lock);
if (class != NULL) {
class->lc_lock(c->c_lock, sharedlock);
if (c_lock != NULL) {
class->lc_lock(c_lock, sharedlock);
/*
* The callout may have been cancelled
* while we switched locks.
*/
if (curr_cancelled) {
class->lc_unlock(c->c_lock);
class->lc_unlock(c_lock);
goto skip;
}
/* The callout cannot be stopped now. */
curr_cancelled = 1;
if (c->c_lock == &Giant.lock_object) {
if (c_lock == &Giant.lock_object) {
gcalls++;
CTR3(KTR_CALLOUT,
"callout %p func %p arg %p",
@ -294,7 +296,7 @@ softclock(void *dummy)
}
#endif
if ((c_flags & CALLOUT_RETURNUNLOCKED) == 0)
class->lc_unlock(c->c_lock);
class->lc_unlock(c_lock);
skip:
mtx_lock_spin(&callout_lock);
curr_callout = NULL;