Messages in this thread Patch in this message | | | Subject | [PATCH] race in mempool_alloc/free | From | Chris Mason <> | Date | Thu, 11 Mar 2004 15:39:04 -0500 |
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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) {
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