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Mon, 21 Dec 2020 08:23:01 -0800 Received: from mtkmbs08n1.mediatek.inc (172.21.101.55) by MTKMBS62N2.mediatek.inc (172.29.193.42) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Mon, 21 Dec 2020 08:22:59 -0800 Received: from mtkcas10.mediatek.inc (172.21.101.39) by mtkmbs08n1.mediatek.inc (172.21.101.55) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Tue, 22 Dec 2020 00:22:49 +0800 Received: from mtksdccf07.mediatek.inc (172.21.84.99) by mtkcas10.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Tue, 22 Dec 2020 00:22:49 +0800 From: Lecopzer Chen To: , Subject: [PATCH v2] arm64: perf: Fix access percpu variables in preemptible context Date: Tue, 22 Dec 2020 00:22:49 +0800 Message-ID: <20201221162249.3119-1-lecopzer.chen@mediatek.com> X-Mailer: git-send-email 2.18.0 MIME-Version: 1.0 X-MTK: N X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201221_112316_639014_A219BECB X-CRM114-Status: GOOD ( 13.11 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mark.rutland@arm.com, sumit.garg@linaro.org, jolsa@redhat.com, catalin.marinas@arm.com, lecopzer.chen@mediatek.com, peterz@infradead.org, will@kernel.org, yj.chiang@mediatek.com, acme@kernel.org, alexander.shishkin@linux.intel.com, mingo@redhat.com, linux-mediatek@lists.infradead.org, namhyung@kernel.org, matthias.bgg@gmail.com, oliver.sang@intel.com, alexandru.elisei@arm.com Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org commit 367c820ef08082 ("arm64: Enable perf events based hard lockup detector") reinitilizes lockup detector after arm64 PMU is initialized and open a window for accessing smp_processor_id() in preemptible context. Since hardlockup_detector_perf_init() always called in init stage with a single cpu, but we initialize lockup detector after the init task is migratable. Fix this by utilizing lockup detector reconfiguration which calls softlockup_start_all() on each cpu and calls watatchdog_nmi_enable() later. Because softlockup_start_all() use IPI call function to make sure watatchdog_nmi_enable() will bind on each cpu and fix this issue. BUG: using smp_processor_id() in preemptible [00000000] code: swapper/0/1 caller is debug_smp_processor_id+0x20/0x2c CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.10.0+ #276 Hardware name: linux,dummy-virt (DT) Call trace: dump_backtrace+0x0/0x3c0 show_stack+0x20/0x6c dump_stack+0x2f0/0x42c check_preemption_disabled+0x1cc/0x1dc debug_smp_processor_id+0x20/0x2c hardlockup_detector_event_create+0x34/0x18c hardlockup_detector_perf_init+0x2c/0x134 watchdog_nmi_probe+0x18/0x24 lockup_detector_init+0x44/0xa8 armv8_pmu_driver_init+0x54/0x78 do_one_initcall+0x184/0x43c kernel_init_freeable+0x368/0x380 kernel_init+0x1c/0x1cc ret_from_fork+0x10/0x30 Fixes: 367c820ef08082 ("arm64: Enable perf events based hard lockup detector") Signed-off-by: Lecopzer Chen Reported-by: kernel test robot Cc: Sumit Garg --- Changelog v1 -> v2: * https://lore.kernel.org/lkml/20201217130617.32202-1-lecopzer.chen@mediatek.com/ * Move solution from kernel/watchdog_hld.c to arm64 perf_event * avoid preemptive kmalloc in preempt_disable(). arch/arm64/kernel/perf_event.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c index 38bb07eff872..c03e21210bbb 100644 --- a/arch/arm64/kernel/perf_event.c +++ b/arch/arm64/kernel/perf_event.c @@ -1345,4 +1345,20 @@ u64 hw_nmi_get_sample_period(int watchdog_thresh) return (u64)max_cpu_freq * watchdog_thresh; } + +/* + * hardlockup_detector_perf_init() always call in init stage with a single + * cpu. In arm64 case, we re-initialize lockup detector after pmu driver + * initialized. Lockup detector initial function use lots of percpu variables + * and this makes CONFIG_DEBUG_PREEMPT unhappy because we are now in + * preemptive context. + * Return 0 if the nmi is ready and register nmi hardlockup detector by + * lockup detector reconfiguration. + */ +int __init watchdog_nmi_probe(void) +{ + if (arm_pmu_irq_is_nmi()) + return 0; + return -ENODEV; +} #endif