lkml.org 
[lkml]   [2004]   [Mar]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Subject[PATCH] race in mempool_alloc/free
From
Date
Hello everyone,

mempool_alloc and mempool_free check pool->curr_nr without any locks
held. This can lead to skipping a wakeup when there are people waiting,
and sleeping when there are free elements in the pool.

I can't trigger this reliably, but sooner or later someone on ppc is
probably going to hit it.

-chris

--- linux.t.orig/mm/mempool.c 2004-03-11 14:34:50.000000000 -0500
+++ linux.t/mm/mempool.c 2004-03-11 14:38:30.000000000 -0500
@@ -203,6 +203,7 @@
* If the pool is less than 50% full and we can perform effective
* page reclaim then try harder to allocate an element.
*/
+ mb();
if ((gfp_mask & __GFP_FS) && (gfp_mask != gfp_nowait) &&
(pool->curr_nr <= pool->min_nr/2)) {
element = pool->alloc(gfp_mask, pool->pool_data);
@@ -230,6 +231,7 @@
blk_run_queues();

prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
+ mb();
if (!pool->curr_nr)
io_schedule();
finish_wait(&pool->wait, &wait);
@@ -250,6 +252,7 @@
{
unsigned long flags;

+ mb();
if (pool->curr_nr < pool->min_nr) {
spin_lock_irqsave(&pool->lock, flags);
if (pool->curr_nr < pool->min_nr) {


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 14:01    [W:2.034 / U:0.008 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site