cpusets alloc GFP_WAIT sleep fix
Subsystems (2)
PATCH 1/1 cpusets alloc GFP_WAIT sleep fix
Linus - please apply.
The cpuset mems_allowed update code in alloc_pages_current could (in theory) put a task to sleep that didn't allow sleeping (did not have __GFP_WAIT flag set). In the rare circumstance that the current tasks mems_generation is outofdate compared to the tasks cpuset mems_generation, this mems_allowed update code needs to grap cpuset_sem, which can sleep.
We avoid this by not trying to update mems_allowed here if we can't sleep (__GFP_WAIT not set).
Applies to top of Linus's bk tree (post 2.6.11)
Thanks to Ray Bryant <[email protected]> for noticing this.
Signed-off-by Paul Jackson <[email protected]>
===================================================================
mm/mempolicy.c +5 -1
@@ -788,12 +788,16 @@ alloc_page_vma(unsigned gfp, struct vm_a* Allocate a page from the kernel page pool. When not in * interrupt context and apply the current process NUMA policy. * Returns NULL when no page can be allocated. +* +* Don't call cpuset_update_current_mems_allowed() unless +* 1) it's ok to take cpuset_sem (can WAIT), and +* 2) allocating for current task (not interrupt). */ struct page *alloc_pages_current (unsigned gfp,unsigned order) {struct mempolicy *pol = current->mempolicy; -if (!in_interrupt ()) +if ((gfp & __GFP_WAIT) && !in_interrupt ())cpuset_update_current_mems_allowed ();if (!pol ||in_interrupt ()) pol = &default_policy;
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Programmer, Linux Scalability
Paul Jackson <[email protected]> 1.650.933.1373, 1.925.600.0401