From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EBA1914884C; Wed, 5 Mar 2025 18:17:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741198634; cv=none; b=WIE1NVidrgPb6O/XrPl8UqEUzkk1Iqig1s6gAvv1ulBLSn7XeoIjwj4lhIpNDj/d/gY3jXImwvQCaUjV//0jOQJFN6pvHg1aU8hclPK4RvNgwcOqzpL8UmlBtINqhXKqhCeSjECinMqT6ahsYTOLx+xdgMcwmhXbigST0KKktMo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741198634; c=relaxed/simple; bh=dG/jBU+VJhnrHtVfpj9SKqP02UnMFNDyzQ9M7Y/a81c=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=GMuU3mVdRYXgH4iXHKphMBQpFCCT059FSUYT89KbhAJj67l4EKdRrOYZy3GqJTXkSJpf2VcIppK0HEJgJCCuga6sh/S8Xg0EtlgXWwbOjkxmhDcX4NVHVumaZo9BCMYq08vHvpNV52UxpzYQKHKue1ZKEiZnk5pk+6M47e8UWXA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=reKufo/U; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="reKufo/U" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1DE8DC4CED1; Wed, 5 Mar 2025 18:17:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1741198633; bh=dG/jBU+VJhnrHtVfpj9SKqP02UnMFNDyzQ9M7Y/a81c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=reKufo/UGM9LDBBo2xyzrNAknwcQrK3lDFjhEq5A1brLwJJoaaFM6fTYw9juNtJ6l 7q8vzYsSx4gzAcIReDFdTDUKdj68hXCftmOSsaxo4nFN0C3cUWHug3oEtZxWghmWqF 5S5bR66V67JBFJ1SonkzQrMpPpBZ6f5L2O2zQ77c= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Luo Gengkun , Ingo Molnar , Kan Liang , Sasha Levin Subject: [PATCH 6.13 064/157] perf/core: Order the PMU list to fix warning about unordered pmu_ctx_list Date: Wed, 5 Mar 2025 18:48:20 +0100 Message-ID: <20250305174507.877792526@linuxfoundation.org> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250305174505.268725418@linuxfoundation.org> References: <20250305174505.268725418@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.13-stable review patch. If anyone has any objections, please let me know. ------------------ From: Luo Gengkun [ Upstream commit 2016066c66192a99d9e0ebf433789c490a6785a2 ] Syskaller triggers a warning due to prev_epc->pmu != next_epc->pmu in perf_event_swap_task_ctx_data(). vmcore shows that two lists have the same perf_event_pmu_context, but not in the same order. The problem is that the order of pmu_ctx_list for the parent is impacted by the time when an event/PMU is added. While the order for a child is impacted by the event order in the pinned_groups and flexible_groups. So the order of pmu_ctx_list in the parent and child may be different. To fix this problem, insert the perf_event_pmu_context to its proper place after iteration of the pmu_ctx_list. The follow testcase can trigger above warning: # perf record -e cycles --call-graph lbr -- taskset -c 3 ./a.out & # perf stat -e cpu-clock,cs -p xxx // xxx is the pid of a.out test.c void main() { int count = 0; pid_t pid; printf("%d running\n", getpid()); sleep(30); printf("running\n"); pid = fork(); if (pid == -1) { printf("fork error\n"); return; } if (pid == 0) { while (1) { count++; } } else { while (1) { count++; } } } The testcase first opens an LBR event, so it will allocate task_ctx_data, and then open tracepoint and software events, so the parent context will have 3 different perf_event_pmu_contexts. On inheritance, child ctx will insert the perf_event_pmu_context in another order and the warning will trigger. [ mingo: Tidied up the changelog. ] Fixes: bd2756811766 ("perf: Rewrite core context handling") Signed-off-by: Luo Gengkun Signed-off-by: Ingo Molnar Reviewed-by: Kan Liang Link: https://lore.kernel.org/r/20250122073356.1824736-1-luogengkun@huaweicloud.com Signed-off-by: Sasha Levin --- kernel/events/core.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index e9f698c08dc17..91c58014fe5dc 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4950,7 +4950,7 @@ static struct perf_event_pmu_context * find_get_pmu_context(struct pmu *pmu, struct perf_event_context *ctx, struct perf_event *event) { - struct perf_event_pmu_context *new = NULL, *epc; + struct perf_event_pmu_context *new = NULL, *pos = NULL, *epc; void *task_ctx_data = NULL; if (!ctx->task) { @@ -5007,12 +5007,19 @@ find_get_pmu_context(struct pmu *pmu, struct perf_event_context *ctx, atomic_inc(&epc->refcount); goto found_epc; } + /* Make sure the pmu_ctx_list is sorted by PMU type: */ + if (!pos && epc->pmu->type > pmu->type) + pos = epc; } epc = new; new = NULL; - list_add(&epc->pmu_ctx_entry, &ctx->pmu_ctx_list); + if (!pos) + list_add_tail(&epc->pmu_ctx_entry, &ctx->pmu_ctx_list); + else + list_add(&epc->pmu_ctx_entry, pos->pmu_ctx_entry.prev); + epc->ctx = ctx; found_epc: -- 2.39.5