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From: Peter Zijlstra <peterz@infradead.org>
To: 王贇 <yun.wang@linux.alibaba.com>
Cc: Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Yonghong Song <yhs@fb.com>,
	John Fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@kernel.org>,
	"open list:PERFORMANCE EVENTS SUBSYSTEM" 
	<linux-perf-users@vger.kernel.org>,
	"open list:PERFORMANCE EVENTS SUBSYSTEM" 
	<linux-kernel@vger.kernel.org>,
	"open list:BPF (Safe dynamic programs and tools)" 
	<netdev@vger.kernel.org>,
	"open list:BPF (Safe dynamic programs and tools)" 
	<bpf@vger.kernel.org>
Subject: Re: [RFC PATCH] perf: fix panic by mark recursion inside perf_log_throttle
Date: Mon, 13 Sep 2021 12:24:24 +0200	[thread overview]
Message-ID: <YT8m2B6D2yWc5Umq@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <f38987a5-dc36-a20d-8c5e-81e8ead5b4dc@linux.alibaba.com>

On Mon, Sep 13, 2021 at 11:00:47AM +0800, 王贇 wrote:
> 
> 
> On 2021/9/10 下午11:38, Peter Zijlstra wrote:
> > On Thu, Sep 09, 2021 at 11:13:21AM +0800, 王贇 wrote:
> >> When running with ftrace function enabled, we observed panic
> >> as below:
> >>
> >>   traps: PANIC: double fault, error_code: 0x0
> >>   [snip]
> >>   RIP: 0010:perf_swevent_get_recursion_context+0x0/0x70
> >>   [snip]
> >>   Call Trace:
> >>    <NMI>
> >>    perf_trace_buf_alloc+0x26/0xd0
> >>    perf_ftrace_function_call+0x18f/0x2e0
> >>    kernelmode_fixup_or_oops+0x5/0x120
> >>    __bad_area_nosemaphore+0x1b8/0x280
> >>    do_user_addr_fault+0x410/0x920
> >>    exc_page_fault+0x92/0x300
> >>    asm_exc_page_fault+0x1e/0x30
> >>   RIP: 0010:__get_user_nocheck_8+0x6/0x13
> >>    perf_callchain_user+0x266/0x2f0
> >>    get_perf_callchain+0x194/0x210
> >>    perf_callchain+0xa3/0xc0
> >>    perf_prepare_sample+0xa5/0xa60
> >>    perf_event_output_forward+0x7b/0x1b0
> >>    __perf_event_overflow+0x67/0x120
> >>    perf_swevent_overflow+0xcb/0x110
> >>    perf_swevent_event+0xb0/0xf0
> >>    perf_tp_event+0x292/0x410
> >>    perf_trace_run_bpf_submit+0x87/0xc0
> >>    perf_trace_lock_acquire+0x12b/0x170
> >>    lock_acquire+0x1bf/0x2e0
> >>    perf_output_begin+0x70/0x4b0
> >>    perf_log_throttle+0xe2/0x1a0
> >>    perf_event_nmi_handler+0x30/0x50
> >>    nmi_handle+0xba/0x2a0
> >>    default_do_nmi+0x45/0xf0
> >>    exc_nmi+0x155/0x170
> >>    end_repeat_nmi+0x16/0x55
> > 
> > kernel/events/Makefile has:
> > 
> > ifdef CONFIG_FUNCTION_TRACER
> > CFLAGS_REMOVE_core.o = $(CC_FLAGS_FTRACE)
> > endif
> > 
> > Which, afaict, should avoid the above, no?
> 
> I'm afraid it's not working for this case, the
> start point of tracing is at lock_acquire() which
> is not from 'kernel/events/core', the following PF
> related function are also not from 'core', prevent
> ftrace on 'core' can't prevent this from happen...

I'm confused tho; where does the #DF come from? Because taking a #PF
from NMI should be perfectly fine.

AFAICT that callchain is something like:

	NMI
	  perf_event_nmi_handler()
	    (part of the chain is missing here)
	      perf_log_throttle()
	        perf_output_begin() /* events/ring_buffer.c */
		  rcu_read_lock()
		    rcu_lock_acquire()
		      lock_acquire()
		        trace_lock_acquire() --> perf_trace_foo

			  ...
			    perf_callchain()
			      perf_callchain_user()
			        #PF (fully expected during a userspace callchain)
				  (some stuff, until the first __fentry)
				    perf_trace_function_call
				      perf_trace_buf_alloc()
				        perf_swevent_get_recursion_context()
					  *BOOM*

Now, supposedly we then take another #PF from get_recursion_context() or
something, but that doesn't make sense. That should just work...

Can you figure out what's going wrong there? going with the RIP, this
almost looks like 'swhash->recursion' goes splat, but again that makes
no sense, that's a per-cpu variable.



  parent reply	other threads:[~2021-09-13 10:24 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-09  3:13 [RFC PATCH] perf: fix panic by mark recursion inside perf_log_throttle 王贇
2021-09-09  6:10 ` 王贇
2021-09-10 15:38 ` Peter Zijlstra
2021-09-13  3:00   ` 王贇
2021-09-13  3:21     ` 王贇
2021-09-13 10:24     ` Peter Zijlstra [this message]
2021-09-13 10:36       ` Peter Zijlstra
2021-09-14  2:02         ` 王贇
2021-09-14  1:58       ` 王贇
2021-09-14 10:28         ` Peter Zijlstra
2021-09-15  1:51           ` 王贇
2021-09-15 15:17             ` [PATCH] x86/dumpstack/64: Add guard pages to stack_info Peter Zijlstra
2021-09-16  3:34               ` 王贇
2021-09-16  3:47               ` 王贇
2021-09-16  8:00                 ` Peter Zijlstra
2021-09-16  8:03                   ` Peter Zijlstra
2021-09-16 10:02                     ` Peter Zijlstra
2021-09-17  2:15                       ` 王贇
2021-09-17  3:02                       ` 王贇
2021-09-17 10:21                         ` Peter Zijlstra
2021-09-17 16:40                           ` Peter Zijlstra
2021-09-18  2:30                             ` 王贇
2021-09-18  6:56                               ` Peter Zijlstra
2021-09-18  2:38                             ` 王贇
2021-09-13  3:30 ` [PATCH] perf: fix panic by disable ftrace on fault.c 王贇
2021-09-13 14:49   ` Dave Hansen
2021-09-14  1:52     ` 王贇
2021-09-14  3:02       ` 王贇
2021-09-14  7:23         ` 王贇
2021-09-14 16:16           ` Dave Hansen
2021-09-15  1:56             ` 王贇
2021-09-15  3:27               ` Dave Hansen
2021-09-15  7:22                 ` 王贇
2021-09-15  7:34                   ` 王贇
2021-09-15 15:19                     ` [PATCH] x86: Increase exception stack sizes Peter Zijlstra
2021-09-16  3:42                       ` 王贇
2021-09-21  7:28                       ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2021-09-21 12:41                       ` tip-bot2 for Peter Zijlstra
2021-09-14  2:08     ` [PATCH] perf: fix panic by disable ftrace on fault.c 王贇

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