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authorShailabh Nagar <nagar@watson.ibm.com>2006-07-14 11:24:47 +0400
committerLinus Torvalds <torvalds@g5.osdl.org>2006-07-15 08:53:57 +0400
commitbb129994c3bff9c5e8df91f05d7e9b6402fbd83f (patch)
tree8d8c4e27af727c9de42ac6aeae04f70537e6bd01 /Documentation/memory-barriers.txt
parentf9fd8914c1acca0d98b69d831b128d5b52f03c51 (diff)
downloadlinux-bb129994c3bff9c5e8df91f05d7e9b6402fbd83f.tar.xz
[PATCH] Remove down_write() from taskstats code invoked on the exit() path
In send_cpu_listeners(), which is called on the exit path, a down_write() was protecting operations like skb_clone() and genlmsg_unicast() that do GFP_KERNEL allocations. If the oom-killer decides to kill tasks to satisfy the allocations,the exit of those tasks could block on the same semphore. The down_write() was only needed to allow removal of invalid listeners from the listener list. The patch converts the down_write to a down_read and defers the removal to a separate critical region. This ensures that even if the oom-killer is called, no other task's exit is blocked as it can still acquire another down_read. Thanks to Andrew Morton & Herbert Xu for pointing out the oom related pitfalls, and to Chandra Seetharaman for suggesting this fix instead of using something more complex like RCU. Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com> Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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