| From 9ee0507e896b45af6d65408c77815800bce30008 Mon Sep 17 00:00:00 2001 |
| From: "Jason A. Donenfeld" <Jason@zx2c4.com> |
| Date: Thu, 22 Sep 2022 18:46:04 +0200 |
| Subject: random: avoid reading two cache lines on irq randomness |
| |
| From: Jason A. Donenfeld <Jason@zx2c4.com> |
| |
| commit 9ee0507e896b45af6d65408c77815800bce30008 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: 58340f8e952b ("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> |
| --- |
| drivers/char/random.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/drivers/char/random.c |
| +++ b/drivers/char/random.c |
| @@ -894,10 +894,10 @@ void __init add_bootloader_randomness(co |
| } |
| |
| 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) = { |
