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From:   =?UTF-8?q?Christoph=20B=C3=B6hmwalder?= 
        <christoph.boehmwalder@linbit.com>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     drbd-dev@lists.linbit.com, linux-kernel@vger.kernel.org,
        Lars Ellenberg <lars.ellenberg@linbit.com>,
        Philipp Reisner <philipp.reisner@linbit.com>,
        linux-block@vger.kernel.org,
        =?UTF-8?q?Christoph=20B=C3=B6hmwalder?= 
        <christoph.boehmwalder@linbit.com>
Subject: [PATCH 1/4] lru_cache: use atomic operations when accessing lc->flags, always
Date:   Tue, 22 Nov 2022 14:42:58 +0100
Message-Id: <20221122134301.69258-2-christoph.boehmwalder@linbit.com>
In-Reply-To: <20221122134301.69258-1-christoph.boehmwalder@linbit.com>
References: <20221122134301.69258-1-christoph.boehmwalder@linbit.com>
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From: Lars Ellenberg <lars.ellenberg@linbit.com>

Or, depending on the way locking is implemented at the call sites,
some updates could be lost (has not been observed).

Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
---
 lib/lru_cache.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/lru_cache.c b/lib/lru_cache.c
index dc35464216d3..fec899386238 100644
--- a/lib/lru_cache.c
+++ b/lib/lru_cache.c
@@ -364,7 +364,7 @@ static struct lc_element *__lc_get(struct lru_cache *lc, unsigned int enr, unsig
 	struct lc_element *e;
 
 	PARANOIA_ENTRY();
-	if (lc->flags & LC_STARVING) {
+	if (test_bit(__LC_STARVING, &lc->flags)) {
 		++lc->starving;
 		RETURN(NULL);
 	}
@@ -417,7 +417,7 @@ static struct lc_element *__lc_get(struct lru_cache *lc, unsigned int enr, unsig
 	 * the LRU element, we have to wait ...
 	 */
 	if (!lc_unused_element_available(lc)) {
-		__set_bit(__LC_STARVING, &lc->flags);
+		set_bit(__LC_STARVING, &lc->flags);
 		RETURN(NULL);
 	}
 
-- 
2.38.1