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| author | Tejun Heo <tj@kernel.org> | 2011-11-21 12:32:23 -0800 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2011-11-21 12:32:23 -0800 |
| commit | 8a32c441c1609f80e55df75422324a1151208f40 (patch) | |
| tree | 73884b06cc2db3ea155af9a88815bb5105a4473e /mm/backing-dev.c | |
| parent | a0acae0e886d44bd5ce6d2f173c1ace0fcf0d9f6 (diff) | |
| download | lwn-8a32c441c1609f80e55df75422324a1151208f40.tar.gz lwn-8a32c441c1609f80e55df75422324a1151208f40.zip | |
freezer: implement and use kthread_freezable_should_stop()
Writeback and thinkpad_acpi have been using thaw_process() to prevent
deadlock between the freezer and kthread_stop(); unfortunately, this
is inherently racy - nothing prevents freezing from happening between
thaw_process() and kthread_stop().
This patch implements kthread_freezable_should_stop() which enters
refrigerator if necessary but is guaranteed to return if
kthread_stop() is invoked. Both thaw_process() users are converted to
use the new function.
Note that this deadlock condition exists for many of freezable
kthreads. They need to be converted to use the new should_stop or
freezable workqueue.
Tested with synthetic test case.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Henrique de Moraes Holschuh <ibm-acpi@hmh.eng.br>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Oleg Nesterov <oleg@redhat.com>
Diffstat (limited to 'mm/backing-dev.c')
| -rw-r--r-- | mm/backing-dev.c | 8 |
1 files changed, 2 insertions, 6 deletions
diff --git a/mm/backing-dev.c b/mm/backing-dev.c index 71034f41a2ba..7ba8feae11b8 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -600,14 +600,10 @@ static void bdi_wb_shutdown(struct backing_dev_info *bdi) /* * Finally, kill the kernel thread. We don't need to be RCU - * safe anymore, since the bdi is gone from visibility. Force - * unfreeze of the thread before calling kthread_stop(), otherwise - * it would never exet if it is currently stuck in the refrigerator. + * safe anymore, since the bdi is gone from visibility. */ - if (bdi->wb.task) { - thaw_process(bdi->wb.task); + if (bdi->wb.task) kthread_stop(bdi->wb.task); - } } /* |