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From: Steven Rostedt <>
To: Stefan Metzmacher <>
Cc: Ingo Molnar <>,,
	io-uring <>,
	"" <>
Subject: Re: sched_waking vs. set_event_pid crash (Re: Tracing busy processes/threads freezes/stalls the whole machine)
Date: Fri, 23 Jul 2021 07:29:06 -0400	[thread overview]
Message-ID: <20210723072906.4f4e7bd5@gandalf.local.home> (raw)
In-Reply-To: <>

On Fri, 23 Jul 2021 12:35:09 +0200
Stefan Metzmacher <> wrote:

> > Assuming this does fix your issue, I sent out a real patch with the
> > explanation of what happened in the change log, so that you can see why
> > that change was your issue.  
> Yes, it does the trick, thanks very much!

Can I get a "Tested-by" from you?

> Now I can finally use:
> trace-cmd record -e all -P $(pidof io_uring-cp-forever)
> But that doesn't include the iou-wrk-* threads
> and the '-c' option seems to only work with forking.

Have you tried it? It should work for threads as well. It hooks to the
sched_process_fork tracepoint, which should be triggered even when a new
thread is created.

Or do you mean that you want that process and all its threads too that are
already running? I could probably have it try to add it via the /proc file
system in that case.

Can you start the task via trace-cmd?

  trace-cmd record -e all -F -c io_uring-cp-forever ...

> Is there a way to specify "trace *all* threads of the given pid"?
> (Note the threads are comming and going, so it's not possible to
> specifiy -P more than once)

Right, although, you could append tasks manually to the set_event_pid file
from another terminal after starting trace-cmd. Once a pid is added to that
file, all children it makes will also be added. That could be a work around
until we have trace-cmd do it.

Care to write a bugzilla report for this feature?

-- Steve

  reply	other threads:[~2021-07-23 11:29 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <>
2021-05-04 12:26 ` Tracing busy processes/threads freezes/stalls the whole machine Stefan Metzmacher
     [not found] ` <20210504092404.6b12aba4@gandalf.local.home>
     [not found]   ` <>
     [not found]     ` <20210504093550.5719d4bd@gandalf.local.home>
     [not found]       ` <>
     [not found]         ` <>
     [not found]           ` <>
2021-07-22 22:43             ` sched_waking vs. set_event_pid crash (Re: Tracing busy processes/threads freezes/stalls the whole machine) Stefan Metzmacher
2021-07-23  1:41               ` Steven Rostedt
2021-07-23  2:51               ` Steven Rostedt
2021-07-23 10:35                 ` Stefan Metzmacher
2021-07-23 11:29                   ` Steven Rostedt [this message]
2021-07-23 11:53                     ` Stefan Metzmacher
2021-07-23 12:41                       ` Steven Rostedt

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