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From: 王贇 <yun.wang@linux.alibaba.com>
To: Peter Zijlstra <peterz@infradead.org>
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: Tue, 14 Sep 2021 10:02:07 +0800	[thread overview]
Message-ID: <6aefb972-3691-2b66-a189-97815df10a12@linux.alibaba.com> (raw)
In-Reply-To: <YT8ptOoN0age04PQ@hirez.programming.kicks-ass.net>



On 2021/9/13 下午6:36, Peter Zijlstra wrote:
> On Mon, Sep 13, 2021 at 12:24:24PM +0200, Peter Zijlstra wrote:
> 
> FWIW:
> 
>> 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
> 
> This function also calls perf_trace_buf_alloc(), and will have
> incremented the recursion count, such that:
> 
>>
>> 			  ...
>> 			    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*
> 
> this one, if it wouldn't mysteriously explode, would find recursion and
> terminate, except that seems to be going side-ways.

Yes, it supposed to avoid recursion in the same context, but it never got
chance to do that, the function and struct should all be fine, any idea
in such situation what can trigger this kind of double fault?

Regards,
Michael Wang

> 
>> 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.
>>
>>

  reply	other threads:[~2021-09-14  2:02 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
2021-09-13 10:36       ` Peter Zijlstra
2021-09-14  2:02         ` 王贇 [this message]
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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