From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DD7FB20F8F for ; Fri, 21 Jul 2023 19:24:46 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 63173C433C8; Fri, 21 Jul 2023 19:24:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1689967486; bh=ETcLymgxzLQXn26PND6ImJaxZ2zQ1tSbxzdIkZ0y2iA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oIjtn9DInvHXp5Pw2xmBwNh9/UjZXacNfXceVRosV1hHSW4sSvDBgOXxzfLNbnElv 9xUcbsZ9hpDchiG3s8P5qXv2ob18SI3526NNTqpRc6kImMUZrhjTq/O65W4uRI8Nf2 b7wRk6IO9UvDbxgsVs5jVgqHad/+gylnupRoOaVw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Eric Lin , Palmer Dabbelt Subject: [PATCH 6.1 180/223] perf: RISC-V: Remove PERF_HES_STOPPED flag checking in riscv_pmu_start() Date: Fri, 21 Jul 2023 18:07:13 +0200 Message-ID: <20230721160528.554309652@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230721160520.865493356@linuxfoundation.org> References: <20230721160520.865493356@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Eric Lin commit 66843b14fb71825fdd73ab12f6594f2243b402be upstream. Since commit 096b52fd2bb4 ("perf: RISC-V: throttle perf events") the perf_sample_event_took() function was added to report time spent in overflow interrupts. If the interrupt takes too long, the perf framework will lower the sysctl_perf_event_sample_rate and max_samples_per_tick. When hwc->interrupts is larger than max_samples_per_tick, the hwc->interrupts will be set to MAX_INTERRUPTS, and events will be throttled within the __perf_event_account_interrupt() function. However, the RISC-V PMU driver doesn't call riscv_pmu_stop() to update the PERF_HES_STOPPED flag after perf_event_overflow() in pmu_sbi_ovf_handler() function to avoid throttling. When the perf framework unthrottled the event in the timer interrupt handler, it triggers riscv_pmu_start() function and causes a WARN_ON_ONCE() warning, as shown below: ------------[ cut here ]------------ WARNING: CPU: 0 PID: 240 at drivers/perf/riscv_pmu.c:184 riscv_pmu_start+0x7c/0x8e Modules linked in: CPU: 0 PID: 240 Comm: ls Not tainted 6.4-rc4-g19d0788e9ef2 #1 Hardware name: SiFive (DT) epc : riscv_pmu_start+0x7c/0x8e ra : riscv_pmu_start+0x28/0x8e epc : ffffffff80aef864 ra : ffffffff80aef810 sp : ffff8f80004db6f0 gp : ffffffff81c83750 tp : ffffaf80069f9bc0 t0 : ffff8f80004db6c0 t1 : 0000000000000000 t2 : 000000000000001f s0 : ffff8f80004db720 s1 : ffffaf8008ca1068 a0 : 0000ffffffffffff a1 : 0000000000000000 a2 : 0000000000000001 a3 : 0000000000000870 a4 : 0000000000000000 a5 : 0000000000000000 a6 : 0000000000000840 a7 : 0000000000000030 s2 : 0000000000000000 s3 : ffffaf8005165800 s4 : ffffaf800424da00 s5 : ffffffffffffffff s6 : ffffffff81cc7590 s7 : 0000000000000000 s8 : 0000000000000006 s9 : 0000000000000001 s10: ffffaf807efbc340 s11: ffffaf807efbbf00 t3 : ffffaf8006a16028 t4 : 00000000dbfbb796 t5 : 0000000700000000 t6 : ffffaf8005269870 status: 0000000200000100 badaddr: 0000000000000000 cause: 0000000000000003 [] riscv_pmu_start+0x7c/0x8e [] perf_adjust_freq_unthr_context+0x15e/0x174 [] perf_event_task_tick+0x88/0x9c [] scheduler_tick+0xfe/0x27c [] update_process_times+0x9a/0xba [] tick_sched_handle+0x32/0x66 [] tick_sched_timer+0x64/0xb0 [] __hrtimer_run_queues+0x156/0x2f4 [] hrtimer_interrupt+0xe2/0x1fe [] riscv_timer_interrupt+0x38/0x42 [] handle_percpu_devid_irq+0x90/0x1d2 [] generic_handle_domain_irq+0x28/0x36 After referring other PMU drivers like Arm, Loongarch, Csky, and Mips, they don't call *_pmu_stop() to update with PERF_HES_STOPPED flag after perf_event_overflow() function nor do they add PERF_HES_STOPPED flag checking in *_pmu_start() which don't cause this warning. Thus, it's recommended to remove this unnecessary check in riscv_pmu_start() function to prevent this warning. Signed-off-by: Eric Lin Link: https://lore.kernel.org/r/20230710154328.19574-1-eric.lin@sifive.com Fixes: 096b52fd2bb4 ("perf: RISC-V: throttle perf events") Cc: stable@vger.kernel.org Signed-off-by: Palmer Dabbelt Signed-off-by: Greg Kroah-Hartman --- drivers/perf/riscv_pmu.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/drivers/perf/riscv_pmu.c b/drivers/perf/riscv_pmu.c index ebca5eab9c9b..56897d4d4fd3 100644 --- a/drivers/perf/riscv_pmu.c +++ b/drivers/perf/riscv_pmu.c @@ -181,9 +181,6 @@ void riscv_pmu_start(struct perf_event *event, int flags) uint64_t max_period = riscv_pmu_ctr_get_width_mask(event); u64 init_val; - if (WARN_ON_ONCE(!(event->hw.state & PERF_HES_STOPPED))) - return; - if (flags & PERF_EF_RELOAD) WARN_ON_ONCE(!(event->hw.state & PERF_HES_UPTODATE)); -- 2.41.0