From ff296293b3538d19278a7f7cd1f3aa600ad9164c Mon Sep 17 00:00:00 2001 From: Stephen Boyd Date: Mon, 19 Aug 2019 08:02:45 -0700 Subject: [PATCH] random: Support freezable kthreads in add_hwgenerator_randomness() The kthread calling this function is freezable after commit 03a3bb7ae631 ("hwrng: core - Freeze khwrng thread during suspend") is applied. Unfortunately, this function uses wait_event_interruptible() but doesn't check for the kthread being woken up by the fake freezer signal. When a user suspends the system, this kthread will wake up and if it fails the entropy size check it will immediately go back to sleep and not go into the freezer. Eventually, suspend will fail because the task never froze and a warning message like this may appear: PM: suspend entry (deep) Filesystems sync: 0.000 seconds Freezing user space processes ... (elapsed 0.001 seconds) done. OOM killer disabled. Freezing remaining freezable tasks ... Freezing of tasks failed after 20.003 seconds (1 tasks refusing to freeze, wq_busy=0): hwrng R running task 0 289 2 0x00000020 [] (__schedule) from [] (schedule+0x3c/0xc0) [] (schedule) from [] (add_hwgenerator_randomness+0xb0/0x100) [] (add_hwgenerator_randomness) from [] (hwrng_fillfn+0xc0/0x14c [rng_core]) [] (hwrng_fillfn [rng_core]) from [] (kthread+0x134/0x148) [] (kthread) from [] (ret_from_fork+0x14/0x2c) Check for a freezer signal here and skip adding any randomness if the task wakes up because it was frozen. This should make the kthread freeze properly and suspend work again. Fixes: 03a3bb7ae631 ("hwrng: core - Freeze khwrng thread during suspend") Reported-by: Keerthy Tested-by: Keerthy Signed-off-by: Stephen Boyd Signed-off-by: Herbert Xu --- drivers/char/random.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index 5d5ea4ce1442..e2e85ca16410 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -2429,6 +2429,7 @@ void add_hwgenerator_randomness(const char *buffer, size_t count, size_t entropy) { struct entropy_store *poolp = &input_pool; + bool frozen = false; if (unlikely(crng_init == 0)) { crng_fast_load(buffer, count); @@ -2439,9 +2440,12 @@ void add_hwgenerator_randomness(const char *buffer, size_t count, * We'll be woken up again once below random_write_wakeup_thresh, * or when the calling thread is about to terminate. */ - wait_event_interruptible(random_write_wait, kthread_should_stop() || + wait_event_interruptible(random_write_wait, + kthread_freezable_should_stop(&frozen) || ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits); - mix_pool_bytes(poolp, buffer, count); - credit_entropy_bits(poolp, entropy); + if (!frozen) { + mix_pool_bytes(poolp, buffer, count); + credit_entropy_bits(poolp, entropy); + } } EXPORT_SYMBOL_GPL(add_hwgenerator_randomness); -- 2.20.1