Re: ppc64* native-gdbserver testsuite hangs on gdb.threads/process-dies-while-handling-bp.exp

[Yao Qi <qiyaoltc@gmail.com>]

Yao Qi <qiyaoltc@gmail.com> writes:

> It is a known issue in GDB, described in PR 18749, rather than a
> regression, so git bisect can't tell you anything useful.  Pedro fixed
> one GDBserver crash caused by 18749, but PR 18749 is still
> there.
>
> I can reproduce the timeout on gcc110,
>
> KFAIL: gdb.threads/process-dies-while-handling-bp.exp: non_stop=on:
> cond_bp_target=0: inferior 1 exited (timeout) (PRMS: gdb/18749)
> Remote debugging from host 127.0.0.1^M
> gdbserver: reading register 10: No such process^M
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> Killing process(es): 15614^M
> monitor exit^M
> Ignoring packet error, continuing...
>
> I think some code path in GDBserver doesn't expect this error.

Does this patch work for you?  With this patch,
process-dies-while-handling-bp.exp never timeout on gcc110 with
native-gdbserver.

-- 
Yao (齐尧)
From ef027cdb366e3000dee2c713abab4f30123d9ed1 Mon Sep 17 00:00:00 2001
From: Yao Qi <yao.qi@linaro.org>
Date: Tue, 19 Dec 2017 17:44:11 +0000
Subject: [PATCH] Mark register unavailable when PTRACE_PEEKUSER fails

As described in PR 18749, GDB/GDBserver may get an error on accessing
memory or register because the thread may disappear.  However, some
path doesn't expect the error.  This patch fixes this problem by
marking the register unavailable when PTRACE_PEEKUSER fails instead
of throwing error.

gdb/gdbserver:

2017-12-19  Yao Qi  <yao.qi@linaro.org>

	PR gdb/18749
	* linux-low.c (fetch_register): Call supply_register instead of
	error.

diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index f6a52d5..0a52a91 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -5555,7 +5555,11 @@ fetch_register (const struct usrregs_info *usrregs,
 		(PTRACE_TYPE_ARG3) (uintptr_t) regaddr, (PTRACE_TYPE_ARG4) 0);
       regaddr += sizeof (PTRACE_XFER_TYPE);
       if (errno != 0)
-	error ("reading register %d: %s", regno, strerror (errno));
+	{
+	  /* Mark register REGNO unavailable.  */
+	  supply_register (regcache, regno, NULL);
+	  return;
+	}
     }
 
   if (the_low_target.supply_ptrace_register)