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/[email protected]/ Signed-off-by: Richard Lyu <[email protected]> --- v2: - Drop the Fixes tag: this is a cleanup, not a bug fix. - Link to v1: https://lore.kernel.org/all/aqIVn0cDBvIYKggE@r1chard/ --- drivers/char/tpm/tpm-interface.c | 6 ------ 1 file changed, 6 deletions(-) diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c index b4e749e70b02..0bab78c8767c 100644 --- a/drivers/char/tpm/tpm-interface.c +++ b/drivers/char/tpm/tpm-interface.c @@ -497,12 +497,6 @@ 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); -- 2.51.0
