cpusets: allow TIF_MEMDIE threads to allocate anywhere
OOM killed tasks have access to memory reserves as specified by the TIF_MEMDIE flag in the hopes that it will quickly exit. If such a task has memory allocations constrained by cpusets, we may encounter a deadlock if a blocking task cannot exit because it cannot allocate the necessary memory. We allow tasks that have the TIF_MEMDIE flag to allocate memory anywhere, including outside its cpuset restriction, so that it can quickly die regardless of whether it is __GFP_HARDWALL. Cc: Andi Kleen <ak@suse.de> Cc: Paul Jackson <pj@sgi.com> Cc: Christoph Lameter <clameter@engr.sgi.com> Signed-off-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -2351,6 +2351,8 @@ static const struct cpuset *nearest_exclusive_ancestor(const struct cpuset *cs)
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* z's node is in our tasks mems_allowed, yes. If it's not a
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* __GFP_HARDWALL request and this zone's nodes is in the nearest
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* mem_exclusive cpuset ancestor to this tasks cpuset, yes.
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* If the task has been OOM killed and has access to memory reserves
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* as specified by the TIF_MEMDIE flag, yes.
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* Otherwise, no.
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*
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* If __GFP_HARDWALL is set, cpuset_zone_allowed_softwall()
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@ -2368,7 +2370,8 @@ static const struct cpuset *nearest_exclusive_ancestor(const struct cpuset *cs)
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* calls get to this routine, we should just shut up and say 'yes'.
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*
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* GFP_USER allocations are marked with the __GFP_HARDWALL bit,
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* and do not allow allocations outside the current tasks cpuset.
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* and do not allow allocations outside the current tasks cpuset
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* unless the task has been OOM killed as is marked TIF_MEMDIE.
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* GFP_KERNEL allocations are not so marked, so can escape to the
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* nearest enclosing mem_exclusive ancestor cpuset.
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*
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@ -2392,6 +2395,7 @@ static const struct cpuset *nearest_exclusive_ancestor(const struct cpuset *cs)
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* affect that:
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* in_interrupt - any node ok (current task context irrelevant)
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* GFP_ATOMIC - any node ok
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* TIF_MEMDIE - any node ok
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* GFP_KERNEL - any node in enclosing mem_exclusive cpuset ok
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* GFP_USER - only nodes in current tasks mems allowed ok.
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*
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@ -2413,6 +2417,12 @@ int __cpuset_zone_allowed_softwall(struct zone *z, gfp_t gfp_mask)
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might_sleep_if(!(gfp_mask & __GFP_HARDWALL));
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if (node_isset(node, current->mems_allowed))
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return 1;
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/*
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* Allow tasks that have access to memory reserves because they have
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* been OOM killed to get memory anywhere.
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*/
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if (unlikely(test_thread_flag(TIF_MEMDIE)))
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return 1;
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if (gfp_mask & __GFP_HARDWALL) /* If hardwall request, stop here */
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return 0;
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@ -2438,7 +2448,9 @@ int __cpuset_zone_allowed_softwall(struct zone *z, gfp_t gfp_mask)
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*
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* If we're in interrupt, yes, we can always allocate.
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* If __GFP_THISNODE is set, yes, we can always allocate. If zone
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* z's node is in our tasks mems_allowed, yes. Otherwise, no.
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* z's node is in our tasks mems_allowed, yes. If the task has been
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* OOM killed and has access to memory reserves as specified by the
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* TIF_MEMDIE flag, yes. Otherwise, no.
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*
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* The __GFP_THISNODE placement logic is really handled elsewhere,
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* by forcibly using a zonelist starting at a specified node, and by
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@ -2462,6 +2474,12 @@ int __cpuset_zone_allowed_hardwall(struct zone *z, gfp_t gfp_mask)
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node = zone_to_nid(z);
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if (node_isset(node, current->mems_allowed))
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return 1;
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/*
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* Allow tasks that have access to memory reserves because they have
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* been OOM killed to get memory anywhere.
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*/
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if (unlikely(test_thread_flag(TIF_MEMDIE)))
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return 1;
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return 0;
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}
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