From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754860AbdKAQrV (ORCPT ); Wed, 1 Nov 2017 12:47:21 -0400 Received: from 19pmail.ess.barracuda.com ([64.235.154.231]:34963 "EHLO 19pmail.ess.barracuda.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754817AbdKAQrS (ORCPT ); Wed, 1 Nov 2017 12:47:18 -0400 From: Matt Redfearn To: Ralf Baechle , James Hogan CC: Matt Redfearn , , Paul Burton , , Ingo Molnar , Paul Burton Subject: [PATCH] MIPS: CPS: Fix use of current_cpu_data in preemptible code Date: Wed, 1 Nov 2017 16:45:56 +0000 Message-ID: <1509554756-16784-1-git-send-email-matt.redfearn@mips.com> X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.150.130.83] X-BESS-ID: 1509554822-452059-3093-511574-1 X-BESS-VER: 2017.12.1-r1710261623 X-BESS-Apparent-Source-IP: 12.201.5.28 X-BESS-Outbound-Spam-Score: 0.00 X-BESS-Outbound-Spam-Report: Code version 3.2, rules version 3.2.2.186483 Rule breakdown below pts rule name description ---- ---------------------- -------------------------------- 0.00 BSF_BESS_OUTBOUND META: BESS Outbound X-BESS-Outbound-Spam-Status: SCORE=0.00 using account:ESS59374 scores of KILL_LEVEL=7.0 tests=BSF_BESS_OUTBOUND X-BESS-BRTS-Status: 1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit 1ec9dd80bedc2 ("MIPS: CPS: Detect CPUs in secondary clusters") added a check in cps_boot_secondary() that the secondary being booted is in the same cluster as the CPU running this code. This check is performed using current_cpu_data without disabling preemption. As such when CONFIG_PREEMPT=y, a BUG is triggered: [ 57.991693] BUG: using smp_processor_id() in preemptible [00000000] code: hotplug/1749 [ 58.063077] Call Trace: [ 58.065842] [<8040cdb4>] show_stack+0x84/0x114 [ 58.070830] [<80b11b38>] dump_stack+0xf8/0x140 [ 58.075796] [<8079b12c>] check_preemption_disabled+0xec/0x118 [ 58.082204] [<80415110>] cps_boot_secondary+0x84/0x44c [ 58.087935] [<80413a14>] __cpu_up+0x34/0x98 [ 58.092624] [<80434240>] bringup_cpu+0x38/0x114 [ 58.097680] [<80434af0>] cpuhp_invoke_callback+0x168/0x8f0 [ 58.103801] [<804362d0>] _cpu_up+0x154/0x1c8 [ 58.108565] [<804363dc>] do_cpu_up+0x98/0xa8 [ 58.113333] [<808261f8>] device_online+0x84/0xc0 [ 58.118481] [<80826294>] online_store+0x60/0x98 [ 58.123562] [<8062261c>] kernfs_fop_write+0x158/0x1d4 [ 58.129196] [<805a2ae4>] __vfs_write+0x4c/0x168 [ 58.134247] [<805a2dc8>] vfs_write+0xe0/0x190 [ 58.139095] [<805a2fe0>] SyS_write+0x68/0xc4 [ 58.143854] [<80415d58>] syscall_common+0x34/0x58 In reality we don't currently support running the kernel on CPUs not in cluster 0, so the answer to cpu_cluster(¤t_cpu_data) will always be 0, even if this task being preempted and continues running on a different CPU. Regardless, the BUG should not be triggered, so fix this by switching to raw_current_cpu_data. When multicluster support lands upstream this check will need removing or changing anyway. Signed-off-by: Matt Redfearn Reviewed-by: Paul Burton CC: linux-mips@linux-mips.org CC: Paul Burton --- arch/mips/kernel/smp-cps.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/mips/kernel/smp-cps.c b/arch/mips/kernel/smp-cps.c index 0063122c85da..8e7a40bcd9d3 100644 --- a/arch/mips/kernel/smp-cps.c +++ b/arch/mips/kernel/smp-cps.c @@ -306,7 +306,7 @@ static int cps_boot_secondary(int cpu, struct task_struct *idle) int err; /* We don't yet support booting CPUs in other clusters */ - if (cpu_cluster(&cpu_data[cpu]) != cpu_cluster(¤t_cpu_data)) + if (cpu_cluster(&cpu_data[cpu]) != cpu_cluster(&raw_current_cpu_data)) return -ENOSYS; vpe_cfg->pc = (unsigned long)&smp_bootstrap; -- 2.7.4