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block: avoid infinite loop in get_task_io_context()

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Calling get_task_io_context() on a exiting task which isn't %current can
loop forever. This triggers at boot time on my dev machine.

BUG: soft lockup - CPU#3 stuck for 22s ! [mountall.1603]

Fix this by making create_task_io_context() returns -EBUSY in this case
to break the loop.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Alan Cox <alan@linux.intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Eric Dumazet 2012-05-31 13:39:05 +02:00 committed by Jens Axboe
parent b77874c969
commit 3c9c708c9f
1 changed files with 5 additions and 1 deletions
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6
block/blk-ioc.c
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@ -235,6 +235,7 @@ void ioc_clear_queue(struct request_queue *q)
int create_task_io_context(struct task_struct *task, gfp_t gfp_flags, int node) int create_task_io_context(struct task_struct *task, gfp_t gfp_flags, int node)
{ {
struct io_context *ioc; struct io_context *ioc;
int ret;
ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO, ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO,
node); node);
@ -262,9 +263,12 @@ int create_task_io_context(struct task_struct *task, gfp_t gfp_flags, int node)
task->io_context = ioc; task->io_context = ioc;
else else
kmem_cache_free(iocontext_cachep, ioc); kmem_cache_free(iocontext_cachep, ioc);
ret = task->io_context ? 0 : -EBUSY;
task_unlock(task); task_unlock(task);
return 0; return ret;
} }
/** /**