RE: Kernel 4.9.x-rt Fully Preemptible Kernel: Issue with gdb and unexpected SIGSTOP signals

From: "Koehrer Mathias (ETAS/ESW5)" <mathias.koehrer@etas.com>
To: "Koehrer Mathias (ETAS/ESW5)" <mathias.koehrer@etas.com>,
	"Sebastian Andrzej Siewior" <bigeasy@linutronix.de>
Cc: linux-rt-users <linux-rt-users@vger.kernel.org>
Subject: RE: Kernel 4.9.x-rt Fully Preemptible Kernel: Issue with gdb and unexpected SIGSTOP signals
Date: Wed, 25 Jan 2017 12:55:30 +0000	[thread overview]
Message-ID: <87521e75b64f4b84b2ecd8b47bb7fe72@FE-MBX1012.de.bosch.com> (raw)
In-Reply-To: <f8526e600a9a45dc959ddf5d12bc430b@FE-MBX1012.de.bosch.com>

Hi Sebastian,
> > > The kernel version 4.1.37-rt43 is working fine, the kernel versions
> > > 4.4.39-rt50 and
> > 4.8.11-rt7 show the same strange behavior as 4.9.0-rt1.
> > > Something on the way between 4.1.37-rt43 and 4.4.39-rt50 seems to
> > > cause the
> > trouble.
> >
> > can you check if one of the earlier v4.4-RT releases (maybe start with
> > -rt2 or -rt1) also shows this behaviour?
> > If not, would you have a testcase?
> I tested with 4.4.0-rt2.
> Here this issue occurs very rarely. I ran the gdb for about 30 times, and here I got
> one hit.
> With the other kernel versions I got the issue in 20-40% of the cases.
> 
> I will try out the other 4.4.0 releases...

I ran more tests. The kernel 4.4.1-rt4 is working fairly fine (only about one hit every 30 runs)
but the kernel 4.4.1-rt5 is causing the issue very often.

Here is a typical output of the gdb command "info thr" for kernel 4.4.1-rt5

[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7ffff3e03700 (LWP 13240)]
[New Thread 0x7ffff3602700 (LWP 13241)]
[New Thread 0x7ffff0933700 (LWP 13266)]
[New Thread 0x7ffff0132700 (LWP 13267)]
[New Thread 0x7fffef931700 (LWP 13268)]
[New Thread 0x7fffef130700 (LWP 13269)]
[New Thread 0x7fffee92f700 (LWP 13270)]
[New Thread 0x7fffee12e700 (LWP 13271)]

Thread 5 "RTPC.bin" received signal SIGSTOP, Stopped (signal).
[Switching to Thread 0x7ffff0132700 (LWP 13267)]
0x00007ffff536124d in read () at ../sysdeps/unix/syscall-template.S:84
84      ../sysdeps/unix/syscall-template.S: No such file or directory.
(gdb) info thr
  Id   Target Id         Frame
  1    Thread 0x7ffff7fd8500 (LWP 13220) "RTPC.bin" clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:80
  2    Thread 0x7ffff3e03700 (LWP 13240) "RTPC.bin" 0x00007ffff536124d in read () at ../sysdeps/unix/syscall-template.S:84
  3    Thread 0x7ffff3602700 (LWP 13241) "RTPC.bin" 0x00007ffff4d902b3 in select () at ../sysdeps/unix/syscall-template.S:84
  4    Thread 0x7ffff0933700 (LWP 13266) "RTPC.bin" 0x00007ffff536124d in read () at ../sysdeps/unix/syscall-template.S:84
* 5    Thread 0x7ffff0132700 (LWP 13267) "RTPC.bin" 0x00007ffff536124d in read () at ../sysdeps/unix/syscall-template.S:84
  6    Thread 0x7fffef931700 (LWP 13268) "RTPC.bin" 0x00007ffff536124d in read () at ../sysdeps/unix/syscall-template.S:84
  7    Thread 0x7fffef130700 (LWP 13269) "RTPC.bin" 0x00007ffff536124d in read () at ../sysdeps/unix/syscall-template.S:84
  8    Thread 0x7fffee92f700 (LWP 13270) "RTPC.bin" 0x00007ffff536124d in read () at ../sysdeps/unix/syscall-template.S:84
  9    Thread 0x7fffee12e700 (LWP 13271) "RTPC.bin" 0x00007ffff536124d in read () at ../sysdeps/unix/syscall-template.S:84
(gdb)

Regards

Mathias