Messages in this thread Patch in this message | | | Date | Wed, 17 Aug 2016 11:19:54 +0200 | From | Peter Zijlstra <> | Subject | [RFC] ftrace / perf 'recursion' |
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blergh, now with LKML added...
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Much like: d525211f9d1b ("perf: Fix irq_work 'tail' recursion")
I found another infinite recursion problem with irq_work:
<IRQ> [<ffffffff811bb985>] ? perf_output_begin_forward+0x5/0x1e0 [<ffffffff81067835>] ? arch_irq_work_raise+0x5/0x40 [<ffffffff811ba170>] ? perf_event_output_forward+0x30/0x60 [<ffffffff81067835>] arch_irq_work_raise+0x5/0x40 [<ffffffff811ab547>] irq_work_queue+0x97/0xa0 [<ffffffff81067835>] ? arch_irq_work_raise+0x5/0x40 [<ffffffff811ab547>] ? irq_work_queue+0x97/0xa0 [<ffffffff811af88f>] __perf_event_overflow+0xcf/0x1b0 [<ffffffff811afa0a>] perf_swevent_overflow+0x9a/0xc0 [<ffffffff811afa8d>] perf_swevent_event+0x5d/0x80 [<ffffffff811b0472>] perf_tp_event+0x1a2/0x1b0 [<ffffffff81a559b0>] ? _raw_spin_trylock+0x30/0x30 [<ffffffff8119dc73>] ? perf_ftrace_function_call+0x83/0xd0 [<ffffffff8117db25>] ? ftrace_ops_assist_func+0xb5/0x110 [<ffffffff8117db25>] ? ftrace_ops_assist_func+0xb5/0x110 [<ffffffff810df52d>] ? do_send_sig_info+0x5d/0x80 [<ffffffff81a559b0>] ? _raw_spin_trylock+0x30/0x30 [<ffffffff8119db3f>] ? perf_trace_buf_alloc+0x1f/0xa0 [<ffffffff8124740b>] ? kill_fasync+0x6b/0x90 [<ffffffff81a559b0>] ? _raw_spin_trylock+0x30/0x30 [<ffffffff8119dc73>] ? perf_ftrace_function_call+0x83/0xd0 [<ffffffff81067753>] ? smp_irq_work_interrupt+0x33/0x40 [<ffffffff810d6f20>] ? irq_enter+0x70/0x70 [<ffffffff8119dcaf>] perf_ftrace_function_call+0xbf/0xd0 [<ffffffff8117db25>] ? ftrace_ops_assist_func+0xb5/0x110 [<ffffffff8117db25>] ftrace_ops_assist_func+0xb5/0x110 [<ffffffff81067753>] ? smp_irq_work_interrupt+0x33/0x40 [<ffffffff810d6f20>] ? irq_enter+0x70/0x70 [<ffffffffa157e077>] 0xffffffffa157e077 [<ffffffff8124740b>] ? kill_fasync+0x6b/0x90 [<ffffffff810d6f25>] ? irq_exit+0x5/0xb0 [<ffffffff810d6f25>] irq_exit+0x5/0xb0 [<ffffffff81067753>] smp_irq_work_interrupt+0x33/0x40 [<ffffffff810d6f25>] ? irq_exit+0x5/0xb0 [<ffffffff81067753>] ? smp_irq_work_interrupt+0x33/0x40 [<ffffffff81a580b9>] irq_work_interrupt+0x89/0x90 <EOI>
Here every irq_work execution triggers another irq_work queue, which gets us stuck in an IRQ loop ad infinitum.
This is through function tracing of irq_exit(), but the same can be done through function tracing of pretty much anything else around there and through the explicit IRQ_WORK_VECTOR tracepoints.
The only 'solution' is something like the below, which I absolutely detest because it makes the irq_work code slower for everyone.
Also, this doesn't fix the problem for any other arch :/
I would much rather tag the whole irq_work thing notrace and remove the tracepoints, but I'm sure that'll not be a popular solution either :/
--- arch/x86/kernel/irq_work.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/irq_work.c b/arch/x86/kernel/irq_work.c index 3512ba607361..a8a7999f1147 100644 --- a/arch/x86/kernel/irq_work.c +++ b/arch/x86/kernel/irq_work.c @@ -10,26 +10,41 @@ #include <asm/apic.h> #include <asm/trace/irq_vectors.h> +/* + * I'm sure header recursion will bite my head off + */ +#ifdef CONFIG_PERF_EVENTS +extern int perf_swevent_get_recursion_context(void); +extern void perf_swevent_put_recursion_context(int rctx); +#else +static inline int perf_swevent_get_recursion_context(void) { return -1; } +static inline void perf_swevent_put_recursion_context(int rctx) { } +#endif + static inline void __smp_irq_work_interrupt(void) { inc_irq_stat(apic_irq_work_irqs); irq_work_run(); } -__visible void smp_irq_work_interrupt(struct pt_regs *regs) +__visible notrace void smp_irq_work_interrupt(struct pt_regs *regs) { + int rctx = perf_swevent_get_recursion_context(); ipi_entering_ack_irq(); __smp_irq_work_interrupt(); exiting_irq(); + perf_swevent_put_recursionn_context(rctx); } -__visible void smp_trace_irq_work_interrupt(struct pt_regs *regs) +__visible notrace void smp_trace_irq_work_interrupt(struct pt_regs *regs) { + int rctx = perf_swevent_get_recursion_context(); ipi_entering_ack_irq(); trace_irq_work_entry(IRQ_WORK_VECTOR); __smp_irq_work_interrupt(); trace_irq_work_exit(IRQ_WORK_VECTOR); exiting_irq(); + perf_swevent_put_recursionn_context(rctx); } void arch_irq_work_raise(void)
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