From: Ingo Molnar mingo@elte.hu
commit b34fbaa9289328c7aec67d2b8b8b7d02bc61c67d upstream.
No need to keep preemption disabled across the whole function.
mix_pool_bytes() uses a spin_lock() to protect the pool and there are other places like write_pool() whhich invoke mix_pool_bytes() without disabling preemption. credit_entropy_bits() is invoked from other places like add_hwgenerator_randomness() without disabling preemption.
Before commit 95b709b6be49 ("random: drop trickle mode") the function used __this_cpu_inc_return() which would require disabled preemption. The preempt_disable() section was added in commit 43d5d3018c37 ("[PATCH] random driver preempt robustness", history tree). It was claimed that the code relied on "vt_ioctl() being called under BKL".
Cc: "Theodore Ts'o" tytso@mit.edu Signed-off-by: Ingo Molnar mingo@elte.hu Signed-off-by: Thomas Gleixner tglx@linutronix.de [bigeasy: enhance the commit message] Signed-off-by: Sebastian Andrzej Siewior bigeasy@linutronix.de Signed-off-by: Theodore Ts'o tytso@mit.edu Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/char/random.c | 4 ---- 1 file changed, 4 deletions(-)
--- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1189,8 +1189,6 @@ static void add_timer_randomness(struct } sample; long delta, delta2, delta3;
- preempt_disable(); - sample.jiffies = jiffies; sample.cycles = random_get_entropy(); sample.num = num; @@ -1228,8 +1226,6 @@ static void add_timer_randomness(struct * and limit entropy entimate to 12 bits. */ credit_entropy_bits(r, min_t(int, fls(delta>>1), 11)); - - preempt_enable(); }
void add_input_randomness(unsigned int type, unsigned int code,