From: Stephen Boyd swboyd@chromium.org
commit ff296293b3538d19278a7f7cd1f3aa600ad9164c upstream.
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 [<c08c64c4>] (__schedule) from [<c08c6a10>] (schedule+0x3c/0xc0) [<c08c6a10>] (schedule) from [<c05dbd8c>] (add_hwgenerator_randomness+0xb0/0x100) [<c05dbd8c>] (add_hwgenerator_randomness) from [<bf1803c8>] (hwrng_fillfn+0xc0/0x14c [rng_core]) [<bf1803c8>] (hwrng_fillfn [rng_core]) from [<c015abec>] (kthread+0x134/0x148) [<c015abec>] (kthread) from [<c01010e8>] (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 j-keerthy@ti.com Tested-by: Keerthy j-keerthy@ti.com Signed-off-by: Stephen Boyd swboyd@chromium.org Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/char/random.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)
--- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -2420,6 +2420,7 @@ void add_hwgenerator_randomness(const ch size_t entropy) { struct entropy_store *poolp = &input_pool; + bool frozen = false;
if (unlikely(crng_init == 0)) { crng_fast_load(buffer, count); @@ -2430,9 +2431,12 @@ void add_hwgenerator_randomness(const ch * 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);