| From | Kamal Mostafa <> | Subject | [PATCH 3.13 119/163] workqueue: apply __WQ_ORDERED to create_singlethread_workqueue() | Date | Thu, 9 Oct 2014 14:02:24 -0700 |
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3.13.11.9 -stable review patch. If anyone has any objections, please let me know.
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From: Tejun Heo <tj@kernel.org>
commit e09c2c295468476a239d13324ce9042ec4de05eb upstream.
create_singlethread_workqueue() is a compat interface for single threaded workqueue which maps to ordered workqueue w/ rescuer in the current implementation. create_singlethread_workqueue() currently implemented by invoking alloc_workqueue() w/ appropriate parameters.
8719dceae2f9 ("workqueue: reject adjusting max_active or applying attrs to ordered workqueues") introduced __WQ_ORDERED to protect ordered workqueues against dynamic attribute changes which can break ordering guarantees but forgot to apply it to create_singlethread_workqueue(). This in itself is okay as nobody currently uses dynamic attribute change on workqueues created with create_singlethread_workqueue().
However, 4c16bd327c ("workqueue: implement NUMA affinity for unbound workqueues") broke singlethreaded guarantee for ordered workqueues through allocating a separate pool_workqueue on each NUMA node by default. A later change 8a2b75384444 ("workqueue: fix ordered workqueues in NUMA setups") fixed it by allocating only one global pool_workqueue if __WQ_ORDERED is set.
Combined, the __WQ_ORDERED omission in create_singlethread_workqueue() became critical breaking its single threadedness and ordering guarantee.
Let's make create_singlethread_workqueue() wrap alloc_ordered_workqueue() instead so that it inherits __WQ_ORDERED and can implicitly track future ordered_workqueue changes.
v2: I missed that __WQ_ORDERED now protects against pwq splitting across NUMA nodes and incorrectly described the patch as a nice-to-have fix to protect against future dynamic attribute usages. Oleg pointed out that this is actually a critical breakage due to 8a2b75384444 ("workqueue: fix ordered workqueues in NUMA setups").
Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Mike Anderson <mike.anderson@us.ibm.com> Cc: Oleg Nesterov <onestero@redhat.com> Cc: Gustavo Luiz Duarte <gduarte@redhat.com> Cc: Tomas Henzl <thenzl@redhat.com> Fixes: 4c16bd327c ("workqueue: implement NUMA affinity for unbound workqueues") Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- include/linux/workqueue.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h index 594521b..eff358e 100644 --- a/include/linux/workqueue.h +++ b/include/linux/workqueue.h @@ -455,7 +455,7 @@ __alloc_workqueue_key(const char *fmt, unsigned int flags, int max_active, alloc_workqueue("%s", WQ_FREEZABLE | WQ_UNBOUND | WQ_MEM_RECLAIM, \ 1, (name)) #define create_singlethread_workqueue(name) \ - alloc_workqueue("%s", WQ_UNBOUND | WQ_MEM_RECLAIM, 1, (name)) + alloc_ordered_workqueue("%s", WQ_MEM_RECLAIM, name) extern void destroy_workqueue(struct workqueue_struct *wq); -- 1.9.1
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