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Wed, 03 Jun 2026 06:28:01 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (smtpav02.fra02v.mail.ibm.com [10.20.54.101]) by smtprelay01.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 6536Rv4E30278130 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 3 Jun 2026 06:27:57 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7BF642004B; Wed, 3 Jun 2026 06:27:57 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 62AD320040; Wed, 3 Jun 2026 06:27:54 +0000 (GMT) Received: from aboo.ibm.com.com (unknown [9.39.24.39]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 3 Jun 2026 06:27:54 +0000 (GMT) From: Aboorva Devarajan To: Madhavan Srinivasan , linuxppc-dev@lists.ozlabs.org Cc: Athira Rajeev , Aboorva Devarajan , Christophe Leroy , linux-kernel@vger.kernel.org, Sourabh Jain , Ritesh Harjani , Shrikanth Hegde Subject: [PATCH 1/3] powerpc/perf: fix preempt count underflow in fsl_emb_pmu_del Date: Wed, 3 Jun 2026 11:57:41 +0530 Message-ID: <20260603062743.1152253-2-aboorvad@linux.ibm.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260603062743.1152253-1-aboorvad@linux.ibm.com> References: <20260603062743.1152253-1-aboorvad@linux.ibm.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjAzMDA1NiBTYWx0ZWRfX4c1QArWfljhH o9R9K7dW9Pey/MGA9b+oGdXCI+tuKtbmTAXv8oe0dgw2Gj/lBO6dz2++Wqgo/l0L+zke/q6WgeH /nxmYQq3kPO2A8R5ZorDcKTXnq5Rk+LyRGdGZ6FJD2n4pwruApBYyRNJLoIM2Cd2rdlRfYoJNYk Mt5bz9PFZOP/tH0meTptlyaBExOCxMcMqdKO869z4zqnhFhx4w8GQUdiBzjsP8Lqt5JQGm57bkL 1byzGJYLEPZrHtRS3Or1A0SBqyaQ8XctF5ZqvtBA4ip/qJhV6xg+RhrwaspBtFPwIyKsQQ3oEDp e5DWT8cq+n9mOF8O9F1zuO6e2hTCg0PHBId4NkXyYpUIZ1HIXcX+rNxTPk8Xln628CCCPCqUXdu XXtkpnLJj3clKp6KIcTNCaecHWa6EreaVw7hzgY7sMPu7PrMnrZOg9kOIrJRAMeHG2h2Wz9cmDC 6QFSyc07BWaJlUhgzRQ== X-Proofpoint-ORIG-GUID: xs-p6tdLRBKDoLyAJ8WU9_8v9dRYH4Cc X-Authority-Analysis: v=2.4 cv=cOzQdFeN c=1 sm=1 tr=0 ts=6a1fc972 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VnNF1IyMAAAA:8 a=-qzNKB2iBSQ2TZesQmUA:9 X-Proofpoint-GUID: pbHtMBC4par7jfvnfN5FHAKH4ZukmdfW X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-03_02,2026-05-28_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 impostorscore=0 lowpriorityscore=0 spamscore=0 bulkscore=0 malwarescore=0 phishscore=0 suspectscore=0 priorityscore=1501 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2606030056 fsl_emb_pmu_del() unconditionally calls put_cpu_var(cpu_hw_events) at the 'out:' label, but only calls the matching get_cpu_var() after the 'i < 0' early-return check. When event->hw.idx is negative the function jumps to 'out:' without having taken get_cpu_var(), and the trailing put_cpu_var() then issues an unmatched preempt_enable(), underflowing preempt_count. On a CONFIG_PREEMPT=y kernel preempt_count would underflow and eventually present as a 'scheduling while atomic' BUG. Move put_cpu_var() to pair with get_cpu_var() so the percpu access is correctly bracketed and the 'out:' label only handles perf_pmu_enable. Fixes: a11106544f33 ("powerpc/perf: e500 support") Reviewed-by: Shrikanth Hegde Signed-off-by: Aboorva Devarajan --- arch/powerpc/perf/core-fsl-emb.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/perf/core-fsl-emb.c b/arch/powerpc/perf/core-fsl-emb.c index 7120ab20cbfe..02b5dd74c187 100644 --- a/arch/powerpc/perf/core-fsl-emb.c +++ b/arch/powerpc/perf/core-fsl-emb.c @@ -366,9 +366,10 @@ static void fsl_emb_pmu_del(struct perf_event *event, int flags) cpuhw->n_events--; + put_cpu_var(cpu_hw_events); + out: perf_pmu_enable(event->pmu); - put_cpu_var(cpu_hw_events); } static void fsl_emb_pmu_start(struct perf_event *event, int ef_flags) -- 2.54.0