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tpm: Remove ineffective wmb() from tpm_pm_resume()

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The comment above the wmb() in tpm_pm_resume() states that the barrier
guarantees TPM_CHIP_FLAG_SUSPENDED is written last, so that hwrng does
not activate before the chip has been fully resumed.  It cannot do so:
it is placed after the store that clears the flag, and therefore does
not order the preceding resume work before that store.  It also has
nothing to pair with, as tpm_try_get_ops() contains no matching read
barrier.

Drop the barrier along with the comment rather than leave a no-op
behind.  Should such ordering turn out to be needed, it would require
paired barriers or locking.

Link: https://lore.kernel.org/all/a62fc816-259a-4d28-a265-e425bc17ed50@gmail.com/
Signed-off-by: Richard Lyu <richard.lyu@suse.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lore.kernel.org/r/20260910024430.40418-1-richard.lyu@suse.com
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
This commit is contained in:
Richard Lyu 2026-09-10 10:44:31 +08:00 committed by Jarkko Sakkinen
parent 313acd594a
commit a32b7973d6
1 changed files with 0 additions and 6 deletions
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6
drivers/char/tpm/tpm-interface.c
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@ -498,12 +498,6 @@ int tpm_pm_resume(struct device *dev)
chip->flags &= ~TPM_CHIP_FLAG_SUSPENDED;
/*
* Guarantee that SUSPENDED is written last, so that hwrng does not
* activate before the chip has been fully resumed.
*/
wmb();
return 0;
}
EXPORT_SYMBOL_GPL(tpm_pm_resume);