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random: remove preempt disabled region

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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>
This commit is contained in:
Ingo Molnar 2018-07-22 10:51:50 -04:00 committed by Greg Kroah-Hartman
parent 933dd2f9aa
commit a5471125ee
1 changed files with 0 additions and 4 deletions
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4
drivers/char/random.c
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@ -1189,8 +1189,6 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
} 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 timer_rand_state *state, unsigned num)
* 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,