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.
Fixes: 99d464506255 ("tpm: Prevent hwrng from activating during resume")
Link:
https://lore.kernel.org/all/[email protected]/
Signed-off-by: Richard Lyu <[email protected]>
---
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
