All of lore.kernel.org
 help / color / mirror / Atom feed
From: Peter Zijlstra <peterz@infradead.org>
To: Song Liu <songliubraving@fb.com>
Cc: "kasong@redhat.com" <kasong@redhat.com>,
	lkml <linux-kernel@vger.kernel.org>,
	Kernel Team <Kernel-team@fb.com>,
	Josh Poimboeuf <jpoimboe@redhat.com>
Subject: Re: Getting empty callchain from perf_callchain_kernel()
Date: Fri, 17 May 2019 09:46:00 +0200	[thread overview]
Message-ID: <20190517074600.GJ2623@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <3CD3EE63-0CD2-404A-A403-E11DCF2DF8D9@fb.com>

On Thu, May 16, 2019 at 11:51:55PM +0000, Song Liu wrote:
> Hi, 
> 
> We found a failure with selftests/bpf/tests_prog in test_stacktrace_map (on bpf/master
> branch). 
> 
> After digging into the code, we found that perf_callchain_kernel() is giving empty
> callchain for tracepoint sched/sched_switch. And it seems related to commit
> 
> d15d356887e770c5f2dcf963b52c7cb510c9e42d
> ("perf/x86: Make perf callchains work without CONFIG_FRAME_POINTER")
> 
> Before this commit, perf_callchain_kernel() returns callchain with regs->ip. With
> this commit, regs->ip is not sent for !perf_hw_regs(regs) case. 

So while I think the below is indeed right; we should store regs->ip
regardless of the unwind path chosen, I still think there's something
fishy if this results in just the 1 entry.

The sched/sched_switch event really should have a non-trivial stack.

Let me see if I can reproduce with just perf.

  reply	other threads:[~2019-05-17  7:46 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-16 23:51 Getting empty callchain from perf_callchain_kernel() Song Liu
2019-05-17  7:46 ` Peter Zijlstra [this message]
2019-05-17  8:10   ` Peter Zijlstra
2019-05-17  8:15     ` Kairui Song
2019-05-17  8:32       ` Kairui Song
2019-05-17 16:22         ` Song Liu
2019-05-17  9:10       ` Peter Zijlstra
2019-05-17 18:40         ` Song Liu
2019-05-17 21:06           ` Alexei Starovoitov
2019-05-17 21:48             ` Song Liu
2019-05-19 18:07               ` Kairui Song
2019-05-20 17:22                 ` Song Liu
2019-05-22 13:51                   ` Peter Zijlstra
2019-05-19 18:06         ` Kairui Song
2019-05-20 17:16           ` Song Liu
2019-05-20 17:19           ` Song Liu
2019-05-22 14:02           ` Peter Zijlstra
2019-05-22 14:49             ` Alexei Starovoitov
2019-05-22 17:45               ` Josh Poimboeuf
2019-05-22 23:46                 ` Josh Poimboeuf
2019-05-23  6:48                   ` Kairui Song
2019-05-23  8:27                     ` Song Liu
2019-05-23  9:11                       ` Kairui Song
2019-05-23 13:32                     ` Josh Poimboeuf
2019-05-23 14:50                       ` Kairui Song
2019-05-23 15:24                         ` Josh Poimboeuf
2019-05-23 16:41                           ` Kairui Song
2019-05-23 17:27                             ` Josh Poimboeuf
2019-05-24  2:20                               ` Kairui Song
2019-05-24 23:23                                 ` Josh Poimboeuf
2019-05-27 11:57                                   ` Kairui Song
2019-06-06 16:04                                     ` Song Liu
2019-06-06 23:58                                       ` Josh Poimboeuf
2019-06-11 21:03                                       ` Josh Poimboeuf
2019-05-24  8:53                           ` Peter Zijlstra
2019-05-24 13:05                             ` Josh Poimboeuf
2019-06-12  3:05                             ` Josh Poimboeuf
2019-06-12  8:54                               ` Peter Zijlstra
2019-06-12 14:50                                 ` Josh Poimboeuf
2019-06-13 20:26                                   ` Josh Poimboeuf
2019-06-12 13:10                               ` Steven Rostedt
2019-06-12 14:26                                 ` Josh Poimboeuf
2019-05-22 18:07       ` Josh Poimboeuf
2019-05-22 21:55         ` Alexei Starovoitov
2019-05-17 16:32     ` Song Liu

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190517074600.GJ2623@hirez.programming.kicks-ass.net \
    --to=peterz@infradead.org \
    --cc=Kernel-team@fb.com \
    --cc=jpoimboe@redhat.com \
    --cc=kasong@redhat.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=songliubraving@fb.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.