From bb129994c3bff9c5e8df91f05d7e9b6402fbd83f Mon Sep 17 00:00:00 2001 From: Shailabh Nagar Date: Fri, 14 Jul 2006 00:24:47 -0700 Subject: [PATCH] [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 Signed-off-by: Shailabh Nagar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Reading git-format-patch failed