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Wed, 03 Sep 2025 00:51:57 -0700 (PDT) Received: from localhost.localdomain ([2a12:a301:1000::20f3]) by smtp.gmail.com with ESMTPSA id 3f1490d57ef6-e9bbe08c80bsm1288391276.29.2025.09.03.00.51.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Sep 2025 00:51:57 -0700 (PDT) From: Jinchao Wang To: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , "Liang, Kan" , linux-perf-users@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Jinchao Wang Subject: [PATCH 1/3] perf/hw_breakpoint: Optimize __modify_bp_slot() handling Date: Wed, 3 Sep 2025 15:51:38 +0800 Message-ID: <20250903075144.3722848-1-wangjinchao600@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Reserve the new slot first, then release the old one to maintain consistency and avoid transient failures. Signed-off-by: Jinchao Wang --- This patch supersedes the previous version: https://lore.kernel.org/all/20250902091759.590664-1-wangjinchao600@gmail.com/ --- kernel/events/hw_breakpoint.c | 19 +++++-------------- 1 file changed, 5 insertions(+), 14 deletions(-) diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c index 8ec2cb688903..6066aff38eec 100644 --- a/kernel/events/hw_breakpoint.c +++ b/kernel/events/hw_breakpoint.c @@ -626,22 +626,13 @@ static int __modify_bp_slot(struct perf_event *bp, u64 old_type, u64 new_type) { int err; - __release_bp_slot(bp, old_type); - err = __reserve_bp_slot(bp, new_type); - if (err) { - /* - * Reserve the old_type slot back in case - * there's no space for the new type. - * - * This must succeed, because we just released - * the old_type slot in the __release_bp_slot - * call above. If not, something is broken. - */ - WARN_ON(__reserve_bp_slot(bp, old_type)); - } + if (err) + return err; - return err; + __release_bp_slot(bp, old_type); + + return 0; } static int modify_bp_slot(struct perf_event *bp, u64 old_type, u64 new_type) -- 2.43.0