Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 4.14 009/237] random: remove preempt disabled region | Date | Thu, 23 Jun 2022 18:40:43 +0200 |
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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 @@ -1136,8 +1136,6 @@ static void add_timer_randomness(struct } sample; long delta, delta2, delta3; - preempt_disable(); - sample.jiffies = jiffies; sample.cycles = random_get_entropy(); sample.num = num; @@ -1175,8 +1173,6 @@ 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,
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