From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755720AbdGXV6y (ORCPT ); Mon, 24 Jul 2017 17:58:54 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:52765 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753257AbdGXV6W (ORCPT ); Mon, 24 Jul 2017 17:58:22 -0400 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, Wanpeng Li , Luiz Capitulino , Rik van Riel , "Paul E. McKenney" Subject: [PATCH tip/core/rcu 5/5] EXP: sched/cputime: Fix using smp_processor_id() in preemptible Date: Mon, 24 Jul 2017 14:58:17 -0700 X-Mailer: git-send-email 2.5.2 In-Reply-To: <20170724215758.GA12075@linux.vnet.ibm.com> References: <20170724215758.GA12075@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 17072421-0048-0000-0000-000001C90B89 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007419; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000214; SDB=6.00892377; UDB=6.00446024; IPR=6.00672541; BA=6.00005489; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00016356; XFM=3.00000015; UTC=2017-07-24 21:58:20 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17072421-0049-0000-0000-000041FF960B Message-Id: <1500933497-12612-5-git-send-email-paulmck@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-07-24_13:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=1 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1706020000 definitions=main-1707240335 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Wanpeng Li BUG: using smp_processor_id() in preemptible [00000000] code: 99-trinity/181 caller is debug_smp_processor_id+0x17/0x19 CPU: 0 PID: 181 Comm: 99-trinity Not tainted 4.12.0-01059-g2a42eb9 #1 Call Trace: dump_stack+0x82/0xb8 check_preemption_disabled+0xd1/0xe3 debug_smp_processor_id+0x17/0x19 vtime_delta+0xd/0x2c task_cputime+0x89/0xdb thread_group_cputime+0x11b/0x1ed thread_group_cputime_adjusted+0x1f/0x47 wait_consider_task+0x2a9/0xaf9 ? lock_acquire+0x97/0xa4 do_wait+0xdf/0x1f4 SYSC_wait4+0x8e/0xb5 ? list_add+0x34/0x34 SyS_wait4+0x9/0xb do_syscall_64+0x70/0x82 entry_SYSCALL64_slow_path+0x25/0x25 As Frederic pointed out: | Although those sched_clock_cpu() things seem to only matter when the | sched_clock() is unstable. And that stability is a condition for nohz_full | to work anyway. So probably sched_clock() alone would be enough. This patch fixes it by replacing sched_clock_cpu() in vtime_delta() by sched_clock() to avoid to call smp_processor_id() in preemptible context. Reported-by: Xiaolong Ye Cc: Thomas Gleixner Cc: Luiz Capitulino Cc: Frederic Weisbecker Cc: Rik van Riel Cc: Peter Zijlstra Cc: Ingo Molnar Signed-off-by: Wanpeng Li Signed-off-by: Paul E. McKenney --- kernel/sched/cputime.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 6e3ea4ac1bda..14d2dbf97c53 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -683,7 +683,7 @@ static u64 vtime_delta(struct vtime *vtime) { unsigned long long clock; - clock = sched_clock_cpu(smp_processor_id()); + clock = sched_clock(); if (clock < vtime->starttime) return 0; @@ -814,7 +814,7 @@ void arch_vtime_task_switch(struct task_struct *prev) write_seqcount_begin(&vtime->seqcount); vtime->state = VTIME_SYS; - vtime->starttime = sched_clock_cpu(smp_processor_id()); + vtime->starttime = sched_clock(); write_seqcount_end(&vtime->seqcount); } @@ -826,7 +826,7 @@ void vtime_init_idle(struct task_struct *t, int cpu) local_irq_save(flags); write_seqcount_begin(&vtime->seqcount); vtime->state = VTIME_SYS; - vtime->starttime = sched_clock_cpu(cpu); + vtime->starttime = sched_clock(); write_seqcount_end(&vtime->seqcount); local_irq_restore(flags); } -- 2.5.2