[PATCH 7/9] random: forget lock in lockless accounting

From: Greg Price
Date: Wed Nov 13 2013 - 03:08:54 EST


The only mutable data accessed here is ->entropy_count, but since
902c098a3 ("random: use lockless techniques in the interrupt path")
that member isn't protected by the lock anyway. Since 10b3a32d2
("random: fix accounting race condition") we use cmpxchg to protect
our accesses to ->entropy_count here. Drop the use of the lock.

Cc: Jiri Kosina <jkosina@xxxxxxx>
Cc: "Theodore Ts'o" <tytso@xxxxxxx>
Signed-off-by: Greg Price <price@xxxxxxx>
---
drivers/char/random.c | 4 ----
1 file changed, 4 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 5dffca8..1f43f9e 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -974,9 +974,6 @@ static size_t account(struct entropy_store *r, size_t nbytes, int min,
int entropy_count, orig;
size_t ibytes;

- /* Hold lock while accounting */
- spin_lock_irqsave(&r->lock, flags);
-
BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);

/* Can we pull enough? */
@@ -999,7 +996,6 @@ retry:
< random_write_wakeup_thresh)
wakeup_write = 1;
}
- spin_unlock_irqrestore(&r->lock, flags);

trace_debit_entropy(r->name, 8 * ibytes);
if (wakeup_write) {
--
1.8.3.2

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