Revision - bb12999 - [PATCH] Remove down_write() from taskstats code invoked on the [...] - origin: https://github.com/torvalds/linux

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02 December 2023, 22:23:51 UTC

Revision bb129994c3bff9c5e8df91f05d7e9b6402fbd83f authored by Shailabh Nagar on 14 July 2006, 07:24:47 UTC, committed by Linus Torvalds on 15 July 2006, 04:53:57 UTC

[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>

1 parent f9fd891

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Tip revision: bb129994c3bff9c5e8df91f05d7e9b6402fbd83f authored by Shailabh Nagar on 14 July 2006, 07:24:47 UTC
[PATCH] Remove down_write() from taskstats code invoked on the exit() path

Tip revision: bb12999

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[PATCH] Remove down_write() from taskstats code invoked on the exit() path

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