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Add cv_wait_interruptible() function.

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This is a minor extension to the condition variable API to allow
for reasonable signal handling on Linux.  The cv_wait() function by
definition must wait unconditionally for cv_signal()/cv_broadcast()
before waking it.  This makes it impossible to woken by a signal
such as SIGTERM.  The cv_wait_interruptible() function was added
to handle this case.  It behaves identically to cv_wait() with the
exception that it waits interruptibly allowing a signal to wake it
up.  This means you do need to be careful and check issig() after
waking.
This commit is contained in:
Brian Behlendorf 2010-05-14 09:24:51 -07:00
parent 97f8f6d789
commit f752b46eb3
2 changed files with 19 additions and 6 deletions
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5
include/sys/condvar.h
View File

@ -57,8 +57,8 @@ typedef enum { CV_DEFAULT=0, CV_DRIVER } kcv_type_t;
extern void __cv_init(kcondvar_t *cvp, char *name, kcv_type_t type, void *arg);
extern void __cv_destroy(kcondvar_t *cvp);
extern void __cv_wait(kcondvar_t *cvp, kmutex_t *mp);
extern clock_t __cv_timedwait(kcondvar_t *cvp, kmutex_t *mp,
clock_t expire_time);
extern void __cv_wait_interruptible(kcondvar_t *cvp, kmutex_t *mp);
extern clock_t __cv_timedwait(kcondvar_t *cvp, kmutex_t *mp, clock_t exp_time);
extern void __cv_signal(kcondvar_t *cvp);
extern void __cv_broadcast(kcondvar_t *cvp);
@ -71,6 +71,7 @@ extern void __cv_broadcast(kcondvar_t *cvp);
})
#define cv_destroy(cvp) __cv_destroy(cvp)
#define cv_wait(cvp, mp) __cv_wait(cvp, mp)
#define cv_wait_interruptible(cvp, mp) __cv_wait_interruptible(cvp, mp)
#define cv_timedwait(cvp, mp, t) __cv_timedwait(cvp, mp, t)
#define cv_signal(cvp) __cv_signal(cvp)
#define cv_broadcast(cvp) __cv_broadcast(cvp)

20
module/spl/spl-condvar.c
View File

@ -84,8 +84,8 @@ __cv_destroy(kcondvar_t *cvp)
}
EXPORT_SYMBOL(__cv_destroy);
void
__cv_wait(kcondvar_t *cvp, kmutex_t *mp)
static void
cv_wait_common(kcondvar_t *cvp, kmutex_t *mp, int state)
{
DEFINE_WAIT(wait);
ENTRY;
@ -103,8 +103,7 @@ __cv_wait(kcondvar_t *cvp, kmutex_t *mp)
ASSERT(cvp->cv_mutex == mp);
spin_unlock(&cvp->cv_lock);
prepare_to_wait_exclusive(&cvp->cv_event, &wait,
TASK_UNINTERRUPTIBLE);
prepare_to_wait_exclusive(&cvp->cv_event, &wait, state);
atomic_inc(&cvp->cv_waiters);
/* Mutex should be dropped after prepare_to_wait() this
@ -118,8 +117,21 @@ __cv_wait(kcondvar_t *cvp, kmutex_t *mp)
finish_wait(&cvp->cv_event, &wait);
EXIT;
}
void
__cv_wait(kcondvar_t *cvp, kmutex_t *mp)
{
cv_wait_common(cvp, mp, TASK_UNINTERRUPTIBLE);
}
EXPORT_SYMBOL(__cv_wait);
void
__cv_wait_interruptible(kcondvar_t *cvp, kmutex_t *mp)
{
cv_wait_common(cvp, mp, TASK_INTERRUPTIBLE);
}
EXPORT_SYMBOL(__cv_wait_interruptible);
/* 'expire_time' argument is an absolute wall clock time in jiffies.
* Return value is time left (expire_time - now) or -1 if timeout occurred.
*/