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Fri, 25 Jun 2021 05:50:11 +0000 (GMT) Received: from in.ibm.com (unknown [9.85.119.88]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Fri, 25 Jun 2021 05:50:11 +0000 (GMT) Date: Fri, 25 Jun 2021 11:20:09 +0530 From: Bharata B Rao To: Srikar Dronamraju Cc: linux-next@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, LKML , Valentin Schneider , Peter Zijlstra , Ingo Molnar Subject: Re: PowerPC guest getting "BUG: scheduling while atomic" on linux-next-20210623 during secondary CPUs bringup Message-ID: Reply-To: bharata@linux.ibm.com References: <20210625054608.fmwt7lxuhp7inkjx@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210625054608.fmwt7lxuhp7inkjx@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: fego09511Jl2BHF_EjJlLB_hSs1T0pDr X-Proofpoint-GUID: fego09511Jl2BHF_EjJlLB_hSs1T0pDr X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-06-25_01:2021-06-24,2021-06-25 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 mlxlogscore=999 spamscore=0 malwarescore=0 clxscore=1011 lowpriorityscore=0 suspectscore=0 bulkscore=0 adultscore=0 impostorscore=0 priorityscore=1501 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2106250030 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 25, 2021 at 11:16:08AM +0530, Srikar Dronamraju wrote: > * Bharata B Rao [2021-06-24 21:25:09]: > > > A PowerPC KVM guest gets the following BUG message when booting > > linux-next-20210623: > > > > smp: Bringing up secondary CPUs ... > > BUG: scheduling while atomic: swapper/1/0/0x00000000 > > no locks held by swapper/1/0. > > Modules linked in: > > CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.13.0-rc7-next-20210623 > > Call Trace: > > [c00000000ae5bc20] [c000000000badc64] dump_stack_lvl+0x98/0xe0 (unreliable) > > [c00000000ae5bc60] [c000000000210200] __schedule_bug+0xb0/0xe0 > > [c00000000ae5bcd0] [c000000001609e28] __schedule+0x1788/0x1c70 > > [c00000000ae5be20] [c00000000160a8cc] schedule_idle+0x3c/0x70 > > [c00000000ae5be50] [c00000000022984c] do_idle+0x2bc/0x420 > > [c00000000ae5bf00] [c000000000229d88] cpu_startup_entry+0x38/0x40 > > [c00000000ae5bf30] [c0000000000666c0] start_secondary+0x290/0x2a0 > > [c00000000ae5bf90] [c00000000000be54] start_secondary_prolog+0x10/0x14 > > > > > > > > smp: Brought up 2 nodes, 16 CPUs > > numa: Node 0 CPUs: 0-7 > > numa: Node 1 CPUs: 8-15 > > > > This seems to have started from next-20210521 and isn't seen on > > next-20210511. > > > > Bharata, > > I think the regression is due to Commit f1a0a376ca0c ("sched/core: > Initialize the idle task with preemption disabled") > > Can you please try with the above commit reverted? Yes, reverting that commit helps. Regards, Bharata.