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From: Heiner Kallweit <hkallweit1@gmail.com>
To: Shixin Liu <liushixin2@huawei.com>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	"Rafael J. Wysocki" <rafael@kernel.org>
Cc: Linux PM <linux-pm@vger.kernel.org>
Subject: crypto: stm32: Broken RPM changes should be reverted
Date: Sat, 27 Nov 2021 14:39:52 +0100	[thread overview]
Message-ID: <4239b61f-f8c5-462f-2951-fbba2dec8b1d@gmail.com> (raw)

When discussing whether pm_runtime_resume_and_get() should be annotated as
__must_check, I became aware of RPM usage in crypto/stm32.

Following two patches replace usage of pm_runtime_get_sync() with
pm_runtime_resume_and_get() w/o checking the return code.

747bf30fd944 ("crypto: stm32/cryp - Fix PM reference leak on stm32-cryp.c")
1cb3ad701970 ("crypto: stm32/hash - Fix PM reference leak on stm32-hash.c")

This results in RPM usage like the following in stm32_hash_export():

pm_runtime_resume_and_get(hdev->dev);
...
pm_runtime_mark_last_busy(hdev->dev);
pm_runtime_put_autosuspend(hdev->dev);

This is broken. After pm_runtime_resume_and_get() the usage count may be
incremented or not. If not, then the call to pm_runtime_put_autosuspend()
results in exactly the imbalance that the patch claims to fix.

Therefore I think both patches should be reverted, or the return code
of pm_runtime_resume_and_get() has to be checked and properly handled
in the driver logic.

             reply	other threads:[~2021-11-27 13:42 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-27 13:39 Heiner Kallweit [this message]
2021-12-01  6:30 ` crypto: stm32 - Revert broken pm_runtime_resume_and_get changes Herbert Xu
2021-12-01  6:50   ` Heiner Kallweit
2021-12-01 14:46   ` Rafael J. Wysocki

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