From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.13]) (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 B93E4227BB5; Fri, 6 Feb 2026 03:17:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.13 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770347829; cv=none; b=tduu+O9hwKHB5G+Kwg081rWI2AsNocWU9M5aAXZ6LUMBTir9nld5BTrG77rVy3H6grRbsdQipaVEfGDv9tpJ8tTVBm8Xc9pKMu3JZsRP3p8zp8xux7E2hDrqoT9cg7LzpZ4bk17CoLrYekT+fYlJO1yL2f31wtAgJTHZ9oHdIHY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770347829; c=relaxed/simple; bh=5LDZNNyyCnPp71pGFeYTZQfoJdKmcINsxRXYVfN7Gu0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Ra1iq1ONDWWpepdLIXUMrvMlYN6UKX6L59ii/ZQrqK7N4/vq9uMm/g0eqF9jdBLnLz7WX0w7fICyrCf6padiURguj5HFfVuGtOpSLCQv2QosPB5n4oniB+ItMu+8qWFV2Jy59CD2P5BETmHTCRTbHnF1Ikn4lTDs1eLIHBPncL4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=QRPWmuUs; arc=none smtp.client-ip=198.175.65.13 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="QRPWmuUs" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1770347828; x=1801883828; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=5LDZNNyyCnPp71pGFeYTZQfoJdKmcINsxRXYVfN7Gu0=; b=QRPWmuUsZFxyP37RVoT0BBwKMXUKa9gZDKeJ1vL0wbTZyoeRFBUMjRgC lopU6mM/HZK0/bd6BZbJ9KbT55JdS9loSQRndYy896USsJ041M8MX9FND aHict6wVp8ReY6BB+UAOvs80ItM9dCQwmQNFUQUOPG0nivZbusTiCDnEe SPlngxNSRdG2Dc/ais8AQ0NuebG/vFU3HsGL5XZJyiXzFWZ1g4iz/R9+5 qL4qOe26PS4VjK7JaYfhDzu418EvpvnrrsZ9hCAjkf2RhMNq1i+w7n2HD kdoZZQ8dl3Lf6WK+TcNzzgTmnuXFEzsCy9w+cMmWdMEswp2bFXakcY02V w==; X-CSE-ConnectionGUID: SogVCVTuSuqN3TWwzMey3A== X-CSE-MsgGUID: tG/3y92oQemfuCD605OMvw== X-IronPort-AV: E=McAfee;i="6800,10657,11692"; a="82670906" X-IronPort-AV: E=Sophos;i="6.21,275,1763452800"; d="scan'208";a="82670906" Received: from fmviesa006.fm.intel.com ([10.60.135.146]) by orvoesa105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Feb 2026 19:17:08 -0800 X-CSE-ConnectionGUID: RS9OFwwbQeWq+eS+u/AScw== X-CSE-MsgGUID: GI/62QlQRceyRvrQLNKUdg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.21,275,1763452800"; d="scan'208";a="210130471" Received: from dapengmi-mobl1.ccr.corp.intel.com (HELO [10.124.240.14]) ([10.124.240.14]) by fmviesa006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Feb 2026 19:17:06 -0800 Message-ID: <0ec3cdd7-d845-4377-9b67-d48668fda4a7@linux.intel.com> Date: Fri, 6 Feb 2026 11:17:03 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [WARNING] WARNING in x86_pmu_stop() (arch/x86/events/core.c:1624) triggered by syzkaller repro To: =?UTF-8?B?5piv5Y+C5beu?= , "linux-perf-users@vger.kernel.org" , "x86@kernel.org" Cc: "linux-kernel@vger.kernel.org" , "peterz@infradead.org" , "dave.hansen@linux.intel.com" , "bp@alien8.de" , "acme@kernel.org" References: Content-Language: en-US From: "Mi, Dapeng" In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit I failed to reproduce this issue with the provided "repro.c" file on Intel platforms... I can't imagine what causes this warning, it looks the behavior is correct except there are some race conditions on the cpuc->active_mask bitmap setting/clearing. On 2/4/2026 9:11 PM, 是参差 wrote: > Hi, > I’m reporting a reproducible WARNING observed in the x86 perf PMU stop path. > The WARNING is triggered by a syzkaller C reproducer that performs multiple perf_event_open() calls with high-frequency sampling settings and then exercises a workload that heavily hits perf/tracepoint paths (e.g., sched tracepoints). The kernel hits a WARN in x86_pmu_stop() while handling perf event throttling/overflow. > The WARNING report points to: > WARNING: arch/x86/events/core.c:1624 at x86_pmu_stop+0x247/0x260, CPU#0: syz.2.7419/25339 > Call trace (trimmed to the perf-relevant part): > perf_event_throttle.part.0 > __perf_event_account_interrupt > __perf_event_overflow > perf_swevent_overflow > perf_swevent_event > perf_tp_event > perf_trace_run_bpf_submit > perf_trace_sched_stat_runtime > ... > This suggests a possible state-machine inconsistency or corner-case interaction between the perf throttling/overflow handling and the x86 PMU stop path (x86_pmu_stop()), potentially triggered by an unusual perf_event_attr combination and high event rate. > Reproducer: > C reproducer: https://pastebin.com/raw/t9u91hQf > console output: https://pastebin.com/raw/XUw5zuQg > kernel config: https://pastebin.com/raw/dP93yBLn > Kernel: > git tree: torvalds/linux > kernel version: 6.19.0-rc7 #1 VOLUNTARY (QEMU Ubuntu 24.10) > HEAD commit:63804fed149a6750ffd28610c5c1c98cce6bd377 > > > > EXT4-fs (loop2): mounting ext3 file system using the ext4 subsystem > EXT4-fs (loop2): 1 truncate cleaned up > EXT4-fs (loop2): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none. > ------------[ cut here ]------------ > WARNING: arch/x86/events/core.c:1624 at x86_pmu_stop+0x247/0x260 arch/x86/events/core.c:1624, CPU#0: syz.2.7419/25339 > CPU: 0 UID: 0 PID: 25339 Comm: syz.2.7419 Not tainted 6.19.0-rc7 #1 VOLUNTARY > Hardware name: QEMU Ubuntu 24.10 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 > RIP: 0010:x86_pmu_stop+0x247/0x260 arch/x86/events/core.c:1624 > Code: 4c 89 ef e8 9b 59 6e 00 e9 48 ff ff ff 4c 89 ef e8 2e 5a 6e 00 eb 85 4c 89 e7 e8 84 59 6e 00 e9 83 fe ff ff e8 6a 99 3e 00 90 <0f> 0b 90 e9 44 ff ff ff 4c 89 e7 e8 69 59 6e 00 eb 96 0f 1f 80 00 > RSP: 0018:ffff88800bebe868 EFLAGS: 00010012 > RAX: 000000000000797b RBX: ffff888010488000 RCX: ffffc90000390000 > RDX: 0000000000080000 RSI: ffff88802e495640 RDI: 0000000000000002 > RBP: 0000000000000000 R08: ffffffff87073701 R09: ffffffff8120c1a6 > R10: 0000000000000001 R11: ffffffff86e3a6c7 R12: 0000000000000001 > R13: ffff8880104881f8 R14: 0000000000000001 R15: 0000000000000000 > FS: 00007f99e6c976c0(0000) GS:0000000000000000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000200000002000 CR3: 000000005f659000 CR4: 0000000000350ef0 > DR0: 0000200000000080 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 > Call Trace: > > perf_event_throttle.part.0+0x89/0xf0 kernel/events/core.c:2682 > perf_event_throttle kernel/events/core.c:2678 [inline] > perf_event_throttle_group kernel/events/core.c:2700 [inline] > __perf_event_account_interrupt+0x2a6/0x430 kernel/events/core.c:10258 > __perf_event_overflow+0xb6/0xa00 kernel/events/core.c:10405 > perf_swevent_overflow+0xac/0x150 kernel/events/core.c:10545 > perf_swevent_event+0x14d/0x2e0 kernel/events/core.c:10583 > perf_tp_event+0x3b7/0x810 kernel/events/core.c:11090 > perf_trace_run_bpf_submit+0xef/0x180 kernel/events/core.c:11014 > do_perf_trace_sched_stat_runtime include/trace/events/sched.h:553 [inline] > perf_trace_sched_stat_runtime+0x360/0x680 include/trace/events/sched.h:553 > __do_trace_sched_stat_runtime include/trace/events/sched.h:576 [inline] > trace_sched_stat_runtime include/trace/events/sched.h:576 [inline] > update_se+0x39b/0x480 kernel/sched/fair.c:1159 > update_curr+0x71/0x450 kernel/sched/fair.c:1209 > put_prev_entity+0x97/0x1b0 kernel/sched/fair.c:5504 > pick_next_task_fair+0xf7e/0x17b0 kernel/sched/fair.c:8949 > __pick_next_task kernel/sched/core.c:5890 [inline] > pick_next_task kernel/sched/core.c:6426 [inline] > __schedule+0x740/0x1df0 kernel/sched/core.c:6809 > preempt_schedule_common kernel/sched/core.c:7051 [inline] > __cond_resched+0x45/0x70 kernel/sched/core.c:7378 > mutex_lock+0x75/0xe0 kernel/locking/mutex.c:287 > ext4_mb_group_or_file fs/ext4/mballoc.c:5886 [inline] > ext4_mb_initialize_context+0x85e/0xcf0 fs/ext4/mballoc.c:5930 > ext4_mb_new_blocks+0x603/0x3fc0 fs/ext4/mballoc.c:6304 > ext4_alloc_branch fs/ext4/indirect.c:340 [inline] > ext4_ind_map_blocks+0x1635/0x20c0 fs/ext4/indirect.c:635 > ext4_map_create_blocks fs/ext4/inode.c:615 [inline] > ext4_map_blocks+0xb51/0x1350 fs/ext4/inode.c:816 > _ext4_get_block+0x1bb/0x550 fs/ext4/inode.c:916 > ext4_block_write_begin+0x88a/0x1040 fs/ext4/inode.c:1203 > ext4_write_begin+0x75f/0x11d0 fs/ext4/inode.c:1364 > generic_perform_write+0x37d/0x800 mm/filemap.c:4314 > ext4_buffered_write_iter+0x11a/0x430 fs/ext4/file.c:299 > ext4_file_write_iter+0x560/0x1790 fs/ext4/file.c:723 > new_sync_write fs/read_write.c:593 [inline] > vfs_write fs/read_write.c:686 [inline] > vfs_write+0xa66/0xe30 fs/read_write.c:666 > ksys_write+0x120/0x240 fs/read_write.c:738 > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > do_syscall_64+0xa9/0x320 arch/x86/entry/syscall_64.c:94 > entry_SYSCALL_64_after_hwframe+0x4b/0x53 > RIP: 0033:0x7f99e822ebe9 > Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 > RSP: 002b:00007f99e6c97038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 > RAX: ffffffffffffffda RBX: 00007f99e8465fa0 RCX: 00007f99e822ebe9 > RDX: 000000000208e24b RSI: 0000200000000340 RDI: 000000000000000a > RBP: 00007f99e82b1e19 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 > R13: 00007f99e8466038 R14: 00007f99e8465fa0 R15: 00007ffc60f336c8 > > ---[ end trace 0000000000000000 ]--- > > Thanks