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authorSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>2012-01-19 23:25:33 +0100
committerRafael J. Wysocki <rjw@sisk.pl>2012-01-19 23:25:33 +0100
commit72081624d5ad3cf56deb6e727b78c4e7a55e4eec (patch)
tree853ed00967d6567af191fbb85b625638970ce15f /drivers
parent160cb5a97daef0cb894685d84c9d4700bb7cccb4 (diff)
downloadlinux-linaro-stable-72081624d5ad3cf56deb6e727b78c4e7a55e4eec.tar.gz
PM / Hibernate: Rewrite unlock_system_sleep() to fix s2disk regression
Commit 33e638b, "PM / Sleep: Use the freezer_count() functions in [un]lock_system_sleep() APIs" introduced an undesirable change in the behaviour of unlock_system_sleep() since freezer_count() internally calls try_to_freeze() - which we don't need in unlock_system_sleep(). And commit bcda53f, "PM / Sleep: Replace mutex_[un]lock(&pm_mutex) with [un]lock_system_sleep()" made these APIs wide-spread. This caused a regression in suspend-to-disk where snapshot_read() and snapshot_write() were getting frozen due to the try_to_freeze embedded in unlock_system_sleep(), since these functions were invoked when the freezing condition was still in effect. Fix this by rewriting unlock_system_sleep() by open-coding freezer_count() and dropping the try_to_freeze() part. Not only will this fix the regression but this will also ensure that the API only does what it is intended to do, and nothing more, under the hood. While at it, make the code more correct and robust by ensuring that the PF_FREEZER_SKIP flag gets cleared with pm_mutex held, to avoid a race with the freezer. Also, to be on the safer side, open-code freezer_do_not_count() as well (inside lock_system_sleep()), to ensure that any unrelated modification to freezer[_do_not]_count() does not break things again! Reported-and-tested-by: Rafael J. Wysocki <rjw@sisk.pl> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
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