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random: remove preempt disabled region

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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 95b709b6be ("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>
This commit is contained in:
Ingo Molnar 2018-07-22 10:51:50 -04:00 committed by Theodore Ts'o
parent 39a8883a2b
commit b34fbaa928
1 changed files with 0 additions and 4 deletions
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4
drivers/char/random.c
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@ -1131,8 +1131,6 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
} sample; } sample;
long delta, delta2, delta3; long delta, delta2, delta3;
preempt_disable();
sample.jiffies = jiffies; sample.jiffies = jiffies;
sample.cycles = random_get_entropy(); sample.cycles = random_get_entropy();
sample.num = num; sample.num = num;
@ -1170,8 +1168,6 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
* and limit entropy entimate to 12 bits. * and limit entropy entimate to 12 bits.
*/ */
credit_entropy_bits(r, min_t(int, fls(delta>>1), 11)); credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
preempt_enable();
} }
void add_input_randomness(unsigned int type, unsigned int code, void add_input_randomness(unsigned int type, unsigned int code,