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Fix race in rwlock implementation which can occur when 

your task is rescheduled to a different cpu after you've
taken the lock but before calling RW_LOCK_HELD is called.
We need the spinlock to ensure there is a wmb() there.


git-svn-id: https://outreach.scidac.gov/svn/spl/trunk@68 7e1ea52c-4ff2-0310-8f11-9dd32ca42a1c
This commit is contained in:
behlendo 2008-04-07 23:54:34 +00:00
parent 728b9dd800
commit 79f92663e3
2 changed files with 11 additions and 2 deletions
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4
include/sys/rwlock.h
View File

@ -163,6 +163,8 @@ rw_tryenter(krwlock_t *rwlp, krw_t rw)
rwlp->rw_owner = current; rwlp->rw_owner = current;
} }
break; break;
default:
BUG_ON(1);
} }
return result; return result;
@ -193,6 +195,8 @@ rw_enter(krwlock_t *rwlp, krw_t rw)
BUG_ON(rwlp->rw_owner != NULL); BUG_ON(rwlp->rw_owner != NULL);
rwlp->rw_owner = current; rwlp->rw_owner = current;
break; break;
default:
BUG_ON(1);
} }
} }

9
modules/spl/spl-rwlock.c
View File

@ -29,16 +29,21 @@ EXPORT_SYMBOL(__rw_write_held);
int int
__rw_lock_held(krwlock_t *rwlp) __rw_lock_held(krwlock_t *rwlp)
{ {
int rc = 0;
BUG_ON(rwlp->rw_magic != RW_MAGIC); BUG_ON(rwlp->rw_magic != RW_MAGIC);
spin_lock_irq(&(rwlp->rw_sem.wait_lock));
#ifdef CONFIG_RWSEM_GENERIC_SPINLOCK #ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
if (rwlp->rw_sem.activity != 0) { if (rwlp->rw_sem.activity != 0) {
#else #else
if (rwlp->rw_sem.count != 0) { if (rwlp->rw_sem.count != 0) {
#endif #endif
return 1; rc = 1;
} }
return 0; spin_unlock_irq(&(rwlp->rw_sem.wait_lock));
return rc;
} }
EXPORT_SYMBOL(__rw_lock_held); EXPORT_SYMBOL(__rw_lock_held);