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Don't hold the UNIX domain socket subsystem lock over the body of the

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UNIX domain socket garbage collection implementation, as that risks
holding the mutex over potentially sleeping operations (as well as
introducing some nasty lock order issues, etc).  unp_gc() will hold
the lock long enough to do necessary deferal checks and set that it's
running, but then release it until it needs to reset the gc state.

RELENG_5 candidate.

Discussed with:	alfred
This commit is contained in:
Robert Watson 2004-08-25 21:24:36 +00:00
parent b0e7e61135
commit 161a0c7cff
1 changed files with 15 additions and 8 deletions
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23
sys/kern/uipc_usrreq.c
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@ -737,9 +737,10 @@ unp_detach(unp)
* gets them (resulting in a "panic: closef: count < 0").
*/
sorflush(unp->unp_socket);
unp_gc();
}
UNP_UNLOCK();
unp_gc(); /* Will unlock UNP. */
} else
UNP_UNLOCK();
UNP_UNLOCK_ASSERT();
if (unp->unp_addr != NULL)
FREE(unp->unp_addr, M_SONAME);
uma_zfree(unp_zone, unp);
@ -1491,6 +1492,11 @@ out:
return (error);
}
/*
* unp_defer is thread-local during garbage collection, and does not require
* explicit synchronization. unp_gcing prevents other threads from entering
* garbage collection, and perhaps should be an sx lock instead.
*/
static int unp_defer, unp_gcing;
static void
@ -1505,18 +1511,17 @@ unp_gc()
UNP_LOCK_ASSERT();
if (unp_gcing)
if (unp_gcing) {
UNP_UNLOCK();
return;
}
unp_gcing = 1;
unp_defer = 0;
UNP_UNLOCK();
/*
* before going through all this, set all FDs to
* be NOT defered and NOT externally accessible
*/
/*
* XXXRW: Acquiring a sleep lock while holding UNP
* mutex cannot be a good thing.
*/
sx_slock(&filelist_lock);
LIST_FOREACH(fp, &filehead, f_list)
fp->f_gcflag &= ~(FMARK|FDEFER);
@ -1698,6 +1703,8 @@ again:
closef(*fpp, (struct thread *) NULL);
free(extra_ref, M_TEMP);
unp_gcing = 0;
UNP_UNLOCK_ASSERT();
}
void