On 06/18/2014 04:57 PM, Marc Dionne wrote:
Hi,
I've been seeing very reproducible soft lockups with 3.16-rc1 similar
to what is reported here:
http://marc.info/?l=linux-btrfs&m=140290088532203&w=2 , along with the
occasional hard lockup, making it impossible to complete a parallel
build on a btrfs filesystem for the package I work on. This was
working fine just a few days before rc1.
Bisecting brought me to the following commit:
commit bd01ec1a13f9a327950c8e3080096446c7804753
Author: Waiman Long<waiman.l...@hp.com>
Date: Mon Feb 3 13:18:57 2014 +0100
x86, locking/rwlocks: Enable qrwlocks on x86
And sure enough if I revert that commit on top of current mainline,
I'm unable to reproduce the soft lockups and hangs.
Marc
The queue rwlock is fair. As a result, recursive read_lock is not
allowed unless the task is in an interrupt context. Doing recursive
read_lock will hang the process when a write_lock happens somewhere in
between. Are recursive read_lock being done in the btrfs code?
-Longman
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