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Fri, 05 Jun 2026 08:29:32 +0000 (GMT) Received: from smtpav05.fra02v.mail.ibm.com (smtpav05.fra02v.mail.ibm.com [10.20.54.104]) by smtprelay01.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 6558TTev61538658 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 5 Jun 2026 08:29:29 GMT Received: from smtpav05.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 21AF620040; Fri, 5 Jun 2026 08:29:29 +0000 (GMT) Received: from smtpav05.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id F03F120043; Fri, 5 Jun 2026 08:29:26 +0000 (GMT) Received: from aboo.bl1-in.ibm.com (unknown [9.123.14.187]) by smtpav05.fra02v.mail.ibm.com (Postfix) with ESMTP; Fri, 5 Jun 2026 08:29:26 +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 v3 3/3] powerpc/kexec: fix double get_cpu() imbalance in kexec_prepare_cpus Date: Fri, 5 Jun 2026 13:59:12 +0530 Message-ID: <20260605082912.305100-4-aboorvad@linux.ibm.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260605082912.305100-1-aboorvad@linux.ibm.com> References: <20260605082912.305100-1-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: AW1haW4tMjYwNjA1MDA3NyBTYWx0ZWRfX+YM7nanr4TyV tzqeKrKloUK6CerzETUZ6bRoRj3KjbpIkgxd2lZocgAQPYM8BOdDMInKqL4VFZ4ufYzoYkw+QfR WeTZXnH0CUr+P0nz74Fee4gqddW5up7KOSBgd2tQTMDtTwYGOIjRD9N/fG29/9v3f8A3OACDuCm aRU0qSpg4yGZVrJ/pYJSKHrFujlMHoTP35LHL1M7t9MNU4HTS9D7YaNVnd/X/9zWK9DKtC1FuV6 FiTPkvJF1m48Gkfbl9CeNjFEPH0tp/XxnlSyDaZmbfFVChDwChinjqxP+dngyq/SlBzzL9HRboe xnw8ZAa1xOf0IPkDK4Bz4wj/uqchtWhqUzPxZxEd/IP69XF5j8C3rhLFcy6t+TUBjQ+vMmDHoZw KyokuQUOK66cxJ008l2BB7ptAUzquQ99fS2tOUiAdwQrb6c2jNhf6sYkLPXFOsvtAQQVA4UdAtj 6geBXVBCLZYf5u7GLrQ== X-Proofpoint-GUID: w1bjydGki8gRIEYyckWJTZvVLvAEEBmf X-Proofpoint-ORIG-GUID: 6oPV2FUYmr39PCo5uZhBQnXQGYe7h1W_ X-Authority-Analysis: v=2.4 cv=DZknbPtW c=1 sm=1 tr=0 ts=6a2288ee cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=NZuQ31_9CfGeVvh8xa4A:9 a=O8hF6Hzn-FEA:10 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=2026-06-05_01,2026-05-28_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 clxscore=1015 suspectscore=0 impostorscore=0 lowpriorityscore=0 phishscore=0 malwarescore=0 priorityscore=1501 bulkscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2606050077 kexec_prepare_cpus_wait() calls get_cpu() internally to obtain the current CPU id. kexec_prepare_cpus() calls kexec_prepare_cpus_wait() twice -- once for KEXEC_STATE_IRQS_OFF and once for KEXEC_STATE_REAL_MODE -- but only issues a single put_cpu() at the end, leaving preempt_count elevated by one extra nesting level. In practice the imbalance does not trigger a 'scheduling while atomic' splat because the kexec path is a one-way trip: IRQs are already disabled, no schedule() occurs after the leak, and default_machine_kexec() overwrites preempt_count with HARDIRQ_OFFSET before jumping into kexec_sequence() which never returns. However the bookkeeping is still wrong. kexec_prepare_cpus() calls local_irq_disable()/hard_irq_disable() before invoking kexec_prepare_cpus_wait(), so the CPU is already pinned and the get_cpu()/put_cpu() preempt_disable() bracketing is unnecessary. Only the current CPU id is needed, so replace get_cpu() with raw_smp_processor_id() and drop the now-unneeded put_cpu(). Fixes: 1fc711f7ffb0 ("powerpc/kexec: Fix race in kexec shutdown") Signed-off-by: Aboorva Devarajan --- arch/powerpc/kexec/core_64.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/arch/powerpc/kexec/core_64.c b/arch/powerpc/kexec/core_64.c index 825ab8a88f18..58c13a59b93b 100644 --- a/arch/powerpc/kexec/core_64.c +++ b/arch/powerpc/kexec/core_64.c @@ -169,7 +169,7 @@ static void kexec_prepare_cpus_wait(int wait_state) int my_cpu, i, notified=-1; hw_breakpoint_disable(); - my_cpu = get_cpu(); + my_cpu = raw_smp_processor_id(); /* Make sure each CPU has at least made it to the state we need. * * FIXME: There is a (slim) chance of a problem if not all of the CPUs @@ -267,8 +267,6 @@ static void kexec_prepare_cpus(void) /* after we tell the others to go down */ if (ppc_md.kexec_cpu_down) ppc_md.kexec_cpu_down(0, 0); - - put_cpu(); } #else /* ! SMP */ -- 2.54.0