From: Stephen Boyd swboyd@chromium.org
commit 59b569480dc8bb9dce57cdff133853a842dfd805 upstream.
Sebastian reports that after commit ff296293b353 ("random: Support freezable kthreads in add_hwgenerator_randomness()") we can call might_sleep() when the task state is TASK_INTERRUPTIBLE (state=1). This leads to the following warning.
do not call blocking ops when !TASK_RUNNING; state=1 set at [<00000000349d1489>] prepare_to_wait_event+0x5a/0x180 WARNING: CPU: 0 PID: 828 at kernel/sched/core.c:6741 __might_sleep+0x6f/0x80 Modules linked in:
CPU: 0 PID: 828 Comm: hwrng Not tainted 5.3.0-rc7-next-20190903+ #46 RIP: 0010:__might_sleep+0x6f/0x80
Call Trace: kthread_freezable_should_stop+0x1b/0x60 add_hwgenerator_randomness+0xdd/0x130 hwrng_fillfn+0xbf/0x120 kthread+0x10c/0x140 ret_from_fork+0x27/0x50
We shouldn't call kthread_freezable_should_stop() from deep within the wait_event code because the task state is still set as TASK_INTERRUPTIBLE instead of TASK_RUNNING and kthread_freezable_should_stop() will try to call into the freezer with the task in the wrong state. Use wait_event_freezable() instead so that it calls schedule() in the right place and tries to enter the freezer when the task state is TASK_RUNNING instead.
Reported-by: Sebastian Andrzej Siewior bigeasy@linutronix.de Tested-by: Sebastian Andrzej Siewior bigeasy@linutronix.de Cc: Keerthy j-keerthy@ti.com Fixes: ff296293b353 ("random: Support freezable kthreads in add_hwgenerator_randomness()") 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 | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-)
--- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -327,6 +327,7 @@ #include <linux/percpu.h> #include <linux/cryptohash.h> #include <linux/fips.h> +#include <linux/freezer.h> #include <linux/ptrace.h> #include <linux/workqueue.h> #include <linux/irq.h> @@ -2483,7 +2484,6 @@ 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); @@ -2494,13 +2494,11 @@ 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_freezable_should_stop(&frozen) || + wait_event_freezable(random_write_wait, + kthread_should_stop() || ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits); - if (!frozen) { - mix_pool_bytes(poolp, buffer, count); - credit_entropy_bits(poolp, entropy); - } + mix_pool_bytes(poolp, buffer, count); + credit_entropy_bits(poolp, entropy); } EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);