Even though hwrng provides a `wait` parameter, it doesn't work very well when waiting for a long time. There are numerous deadlocks that emerge related to shutdown. Work around this API limitation by waiting for a shorter amount of time and erroring more frequently. This commit also prevents hwrng from splatting messages to dmesg when there's a timeout and switches to using schedule_timeout_interruptible(), so that the kthread can be stopped.
Reported-by: Gregory Erwin gregerwin256@gmail.com Tested-by: Gregory Erwin gregerwin256@gmail.com Cc: Toke Høiland-Jørgensen toke@redhat.com Cc: Kalle Valo kvalo@kernel.org Cc: Rui Salvaterra rsalvaterra@gmail.com Cc: Herbert Xu herbert@gondor.apana.org.au Cc: stable@vger.kernel.org Fixes: fcd09c90c3c5 ("ath9k: use hw_random API instead of directly dumping into random.c") Link: https://lore.kernel.org/all/CAO+Okf6ZJC5-nTE_EJUGQtd8JiCkiEHytGgDsFGTEjs0c00... Link: https://lore.kernel.org/lkml/CAO+Okf5k+C+SE6pMVfPf-d8MfVPVq4PO7EY8Hys_DVXten... Link: https://bugs.archlinux.org/task/75138 Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com --- Sorry for all the churn here in sending a v4 and v5 so soon. The semantics of schedule_timeout_interruptible vs msleep_interruptible with respect to kthreads is kind of confusing. I'll send a follow up patch for that elsewhere. For now I think this should suffice for fixing the bug.
drivers/char/hw_random/core.c | 3 +-- drivers/net/wireless/ath/ath9k/rng.c | 20 +++----------------- 2 files changed, 4 insertions(+), 19 deletions(-)
diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index 16f227b995e8..5309fab98631 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -513,8 +513,7 @@ static int hwrng_fillfn(void *unused) break;
if (rc <= 0) { - pr_warn("hwrng: no data available\n"); - msleep_interruptible(10000); + schedule_timeout_interruptible(HZ * 10); continue; }
diff --git a/drivers/net/wireless/ath/ath9k/rng.c b/drivers/net/wireless/ath/ath9k/rng.c index cb5414265a9b..757603d1949d 100644 --- a/drivers/net/wireless/ath/ath9k/rng.c +++ b/drivers/net/wireless/ath/ath9k/rng.c @@ -52,20 +52,6 @@ static int ath9k_rng_data_read(struct ath_softc *sc, u32 *buf, u32 buf_size) return j << 2; }
-static u32 ath9k_rng_delay_get(u32 fail_stats) -{ - u32 delay; - - if (fail_stats < 100) - delay = 10; - else if (fail_stats < 105) - delay = 1000; - else - delay = 10000; - - return delay; -} - static int ath9k_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait) { struct ath_softc *sc = container_of(rng, struct ath_softc, rng_ops); @@ -80,10 +66,10 @@ static int ath9k_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait) bytes_read += max & 3UL; memzero_explicit(&word, sizeof(word)); } - if (!wait || !max || likely(bytes_read) || fail_stats > 110) + if (!wait || !max || likely(bytes_read) || ++fail_stats >= 100 || + ((current->flags & PF_KTHREAD) && kthread_should_stop()) || + schedule_timeout_interruptible(HZ / 20)) break; - - msleep_interruptible(ath9k_rng_delay_get(++fail_stats)); }
if (wait && !bytes_read && max)