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Date: Mon, 11 Mar 2024 11:34:18 +0100 From: Marco Elver <elver@...gle.com> To: Sebastian Andrzej Siewior <bigeasy@...utronix.de> Cc: linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, Adrian Hunter <adrian.hunter@...el.com>, Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, Ian Rogers <irogers@...gle.com>, Ingo Molnar <mingo@...hat.com>, Jiri Olsa <jolsa@...nel.org>, Mark Rutland <mark.rutland@....com>, Namhyung Kim <namhyung@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de> Subject: Re: [PATCH 0/4] perf: Make SIGTRAP and __perf_pending_irq() work on RT. On Fri, Mar 08, 2024 at 06:51PM +0100, Sebastian Andrzej Siewior wrote: > Hi, > > Arnaldo reported that "perf test sigtrap" fails on PREEMPT_RT. Sending > the signal gets delayed until event_sched_out() which then uses > task_work_add() for its delivery. This breaks on PREEMPT_RT because the > signal is delivered with disabled preemption. > > While looking at this, I also stumbled upon __perf_pending_irq() which > requires disabled interrupts but this is not the case on PREEMPT_RT. > > This series aim to address both issues while not introducing a new issue > at the same time ;) > Any testing is appreciated. Unfortunately there's a bug in it somewhere. It can be reproduced with tools/testing/selftests/perf_events/remove_on_exec. (FWIW, the kselftests in that directory are more aggressive test cases that I never figured out how to properly port to the 'perf test' framework: sigtrap_threads is a more aggressive version of the 'sigtrap' perf test, and remove_on_exec has no perf test counterpart.) $ make headers_install $ cd tools/testing/selftests/perf_events && make $ ./remove_on_exec The test appears to pass, but the kernel log shows a few warnings: [ 40.304858] ------------[ cut here ]------------ [ 40.307147] unexpected event refcount: 2; ptr=ffffa026c7d94100 [ 40.325434] WARNING: CPU: 1 PID: 404 at kernel/events/core.c:5242 perf_event_exit_event+0x1aa/0x1e0 [ 40.329603] Modules linked in: [ 40.331401] CPU: 1 PID: 404 Comm: remove_on_exec Not tainted 6.8.0-00004-g852781317836 #1 [ 40.336013] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 40.340997] RIP: 0010:perf_event_exit_event+0x1aa/0x1e0 [ 40.343374] Code: 5c 41 5d 41 5e 41 5f 5d e9 c3 b6 fe ff e8 3e d5 f7 ff 90 49 8b b6 38 02 00 00 48 c7 c7 6c eb d3 b4 4c 89 f2 e8 f7 66 e0 ff 90 <0f> 0b 90 90 f0 48 ff 8b 38 02 00 00 74 a7 e8 13 d5 f7 ff 5b 41 5c [ 40.352207] RSP: 0000:ffffa4c4c2173c60 EFLAGS: 00010246 [ 40.354952] RAX: 35f6eccd09146400 RBX: ffffa026c7d92f48 RCX: ffffa026c3eba200 [ 40.358539] RDX: 0000000000000000 RSI: ffffffffb4d389e9 RDI: 00000000ffffffff [ 40.362858] RBP: 00000000ffffffff R08: 0000000000000001 R09: 0000000000000003 [ 40.366295] R10: ffffa026c3eba200 R11: ffffffffb3d5caa0 R12: ffffa026c3a31538 [ 40.369540] R13: 0000000000000000 R14: ffffa026c7d94100 R15: ffffa026c3a31400 [ 40.373569] FS: 0000000000000000(0000) GS:ffffa029efc40000(0000) knlGS:0000000000000000 [ 40.377495] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 40.380214] CR2: 000055bd7562b73f CR3: 000000010970e001 CR4: 0000000000770ef0 [ 40.383313] DR0: 000055a5212ab828 DR1: 0000000000000000 DR2: 0000000000000000 [ 40.386447] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 [ 40.389492] PKRU: 55555554 [ 40.390588] Call Trace: [ 40.391568] <TASK> [ 40.392432] ? __warn+0xf6/0x290 [ 40.393736] ? perf_event_exit_event+0x1aa/0x1e0 [ 40.395544] ? report_bug+0x13f/0x1e0 [ 40.397039] ? handle_bug+0x3e/0x70 [ 40.398432] ? exc_invalid_op+0x1a/0x50 [ 40.399960] ? asm_exc_invalid_op+0x1a/0x20 [ 40.401561] ? __pfx_write_msg+0x10/0x10 [ 40.403016] ? perf_event_exit_event+0x1aa/0x1e0 [ 40.404707] perf_event_exec+0x3f5/0x700 [ 40.406172] begin_new_exec+0x720/0x850 [ 40.407589] ? load_elf_phdrs+0x84/0x100 [ 40.409030] load_elf_binary+0x3ba/0xf40 [ 40.410457] ? lock_release+0x23b/0x320 [ 40.411795] ? bprm_execve+0x4f7/0x960 [ 40.413101] bprm_execve+0x502/0x960 [ 40.414341] do_execveat_common+0x23d/0x2a0 [ 40.415699] __x64_sys_execve+0x3a/0x50 [ 40.416948] do_syscall_64+0xf2/0x1d0 [ 40.418281] ? lockdep_hardirqs_on+0x9c/0x150 [ 40.419699] entry_SYSCALL_64_after_hwframe+0x6f/0x77 [ 40.421267] RIP: 0033:0x7f9ccc6749fb [ 40.422400] Code: Unable to access opcode bytes at 0x7f9ccc6749d1. [ 40.424252] RSP: 002b:00007ffd2371f358 EFLAGS: 00000246 ORIG_RAX: 000000000000003b [ 40.426519] RAX: ffffffffffffffda RBX: 00007ffd2371f798 RCX: 00007f9ccc6749fb [ 40.428643] RDX: 00007ffd2371f7a8 RSI: 00007ffd2371f360 RDI: 00005653e364e74a [ 40.430783] RBP: 00007ffd2371f3c0 R08: 00007ffd2371f370 R09: 00007ffd2371f390 [ 40.432924] R10: 00005653e364e73f R11: 0000000000000246 R12: 0000000000000000 [ 40.434964] R13: 00007ffd2371f7a8 R14: 00007f9ccc7ba000 R15: 00005653e3650dd8 [ 40.437052] </TASK> [ 40.437686] irq event stamp: 2323 [ 40.438787] hardirqs last enabled at (2345): [<ffffffffb2f6725c>] console_unlock+0xec/0x1a0 [ 40.441125] hardirqs last disabled at (2356): [<ffffffffb2f67241>] console_unlock+0xd1/0x1a0 [ 40.443386] softirqs last enabled at (2340): [<ffffffffb2ec680f>] __irq_exit_rcu+0x6f/0x100 [ 40.445669] softirqs last disabled at (2333): [<ffffffffb2ec680f>] __irq_exit_rcu+0x6f/0x100 [ 40.447976] ---[ end trace 0000000000000000 ]--- [ 40.474464] ------------[ cut here ]------------ [ 40.474467] WARNING: CPU: 6 PID: 390 at kernel/events/core.c:9595 __perf_event_overflow+0x252/0x270 [ 40.474483] Modules linked in: [ 40.474486] CPU: 6 PID: 390 Comm: remove_on_exec Tainted: G W 6.8.0-00004-g852781317836 #1 [ 40.474492] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 40.474496] RIP: 0010:__perf_event_overflow+0x252/0x270 [ 40.474504] Code: 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc e8 c6 b4 f8 ff 31 ed eb e5 e8 bd b4 f8 ff 90 0f 0b 90 e9 24 ff ff ff e8 af b4 f8 ff 90 <0f> 0b 90 e9 2f ff ff ff e8 a1 b4 f8 ff eb e2 66 66 66 66 66 66 2e [ 40.474510] RSP: 0000:ffffa4c4c20dbc88 EFLAGS: 00010046 [ 40.474514] RAX: ffffffffb30a65b1 RBX: ffffa026c7d90008 RCX: ffffa026c7948040 [ 40.474517] RDX: 0000000080110000 RSI: ffffffffb4e127f5 RDI: ffffffffb4d7dc9a [ 40.474521] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 [ 40.474524] R10: ffffa4c4c20dbd00 R11: ffffffffb2e071c0 R12: 0000003000000063 [ 40.474528] R13: 0000002000000001 R14: ffffa4c4c20dbf58 R15: ffffa4c4c20dbd00 [ 40.474531] FS: 00007f9ccc77d680(0000) GS:ffffa029efd80000(0000) knlGS:0000000000000000 [ 40.474536] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 40.474540] CR2: 00007f9ccc77dfa8 CR3: 0000000104fd8004 CR4: 0000000000770ef0 [ 40.474546] DR0: 000055a5212ab828 DR1: 0000000000000000 DR2: 0000000000000000 [ 40.474549] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 [ 40.474552] PKRU: 55555554 [ 40.474554] Call Trace: [ 40.474556] <TASK> [ 40.474558] ? __warn+0xf6/0x290 [ 40.474570] ? __perf_event_overflow+0x252/0x270 [ 40.474578] ? report_bug+0x13f/0x1e0 [ 40.474588] ? handle_bug+0x3e/0x70 [ 40.474598] ? exc_invalid_op+0x1a/0x50 [ 40.474608] ? asm_exc_invalid_op+0x1a/0x20 [ 40.474622] ? __pfx_perf_event_nmi_handler+0x10/0x10 [ 40.474633] ? __perf_event_overflow+0x251/0x270 [ 40.474641] ? __perf_event_overflow+0x252/0x270 [ 40.474648] ? __perf_event_overflow+0x251/0x270 [ 40.474656] intel_pmu_handle_irq+0x3ab/0xb20 [ 40.474680] ? verify_lock_unused+0xb/0x70 [ 40.474691] ? lock_acquire+0x1ab/0x250 [ 40.474700] ? nmi_handle+0x30/0x310 [ 40.474709] perf_event_nmi_handler+0x2d/0x60 [ 40.474719] ? nmi_handle+0x30/0x310 [ 40.474724] nmi_handle+0xf9/0x310 [ 40.474730] ? trace_rcu_dyntick+0x41/0xe0 [ 40.474738] ? nmi_handle+0x30/0x310 [ 40.474746] default_do_nmi+0x63/0x160 [ 40.474757] exc_nmi+0xbc/0x110 [ 40.474768] asm_exc_nmi+0xb6/0xff [ 40.474773] RIP: 0033:0x5653e364d7c5 [ 40.474777] Code: d4 83 45 c4 01 8b 45 c4 83 f8 1d 0f 86 28 fe ff ff 8b 05 2e 3f 00 00 89 85 2c ff ff ff 90 8b 15 21 3f 00 00 8b 85 2c ff ff ff <39> c2 74 f0 90 90 c9 c3 55 48 89 e5 48 81 ec b0 00 00 00 48 8d 95 [ 40.474782] RSP: 002b:00007ffd2371f3d0 EFLAGS: 00000246 [ 40.474786] RAX: 0000000000000005 RBX: 00007ffd2371f798 RCX: 00007f9ccc5d894b [ 40.474789] RDX: 0000000000000005 RSI: 0000000000000009 RDI: 00000000000001a4 [ 40.474793] RBP: 00007ffd2371f4d0 R08: 0000000000000000 R09: 0000000000000000 [ 40.474796] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 [ 40.474799] R13: 00007ffd2371f7a8 R14: 00007f9ccc7ba000 R15: 00005653e3650dd8 [ 40.474809] </TASK> [ 40.474811] irq event stamp: 27946 [ 40.474812] hardirqs last enabled at (27945): [<ffffffffb458ed78>] exc_nmi+0xc8/0x110 [ 40.474824] hardirqs last disabled at (27946): [<ffffffffb458ed52>] exc_nmi+0xa2/0x110 [ 40.474834] softirqs last enabled at (27854): [<ffffffffb2e59aa9>] fpu__restore_sig+0x229/0x870 [ 40.474844] softirqs last disabled at (27852): [<ffffffffb2e59aa9>] fpu__restore_sig+0x229/0x870 [ 40.474853] ---[ end trace 0000000000000000 ]--- Thanks, -- Marco
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