Re: [BUG] tracing: Too many tries to read user space

[Masami Hiramatsu (Google) <mhiramat@kernel.org>]

On Wed, 8 Jul 2026 09:18:04 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Wed, 8 Jul 2026 21:37:53 +0900
> Jeongho Choi <jh1012.choi@samsung.com> wrote:
> 
> > The code at the WARN location mentioned in the log above is as follows.
> > 
> > 7374                 if (WARN_ONCE(trys++ > 100, "Error: Too many
> >   tries to read user space"))
> > 7375                         return NULL;
> > 
> 
> This happens when something forces a schedule.
> 
> > 
> > Our current analysis is as follows:
> > 
> > In the Gmail process, during a low memory situation, LMKD writes strings
> > to /sys/kernel/tracing/trace_marker for systrace recording. At the same
> > time, it broadcasts a sigkill due to low memory, which is causing the
> > LMKD trace marker operation to stall.
> > 
> 
> Can you see what is being scheduled in? Perhaps use the persistent ring
> buffer (if you can) and enable sched_switch tracepoint in it.

Nit: If the device just caused oom and not crash/reboot the kernel, you can
just use normal ring buffer (or perfetto).

Thanks, 

-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>