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random: avoid reading two cache lines on irq randomness

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commit 9ee0507e89 upstream.

In order to avoid reading and dirtying two cache lines on every IRQ,
move the work_struct to the bottom of the fast_pool struct. add_
interrupt_randomness() always touches .pool and .count, which are
currently split, because .mix pushes everything down. Instead, move .mix
to the bottom, so that .pool and .count are always in the first cache
line, since .mix is only accessed when the pool is full.

Fixes: 58340f8e95 ("random: defer fast pool mixing to worker")
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jason A. Donenfeld
2022-09-22 18:46:04 +02:00
committed by Greg Kroah-Hartman
parent 638f84a718
commit c1a4423fd3
1 changed files with 1 additions and 1 deletions
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2
drivers/char/random.c
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@@ -895,10 +895,10 @@ void __cold add_bootloader_randomness(const void *buf, size_t len)
EXPORT_SYMBOL_GPL(add_bootloader_randomness);
struct fast_pool {
struct work_struct mix;
unsigned long pool[4];
unsigned long last;
unsigned int count;
struct work_struct mix;
};
static DEFINE_PER_CPU(struct fast_pool, irq_randomness) = {