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]>
===================================================================
--- 2.6.12-pj.orig/mm/mempolicy.c 2005-03-16 01:16:58.000000000 -0800
+++ 2.6.12-pj/mm/mempolicy.c 2005-03-16 01:32:05.000000000 -0800
@@ -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;
--
I won't rest till it's the best ...
Programmer, Linux Scalability
Paul Jackson <[EMAIL PROTECTED]> 1.650.933.1373,
1.925.600.0401
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