Fix tid-reuse sometimes blocks for a very long (infinite?) time.

Fix tid-reuse sometimes blocks for a very long (infinite?) time.

A failure that seems to cause a long/infinite time is the following:

For a not clear reason, tid-reuse.c spawner thread sometimes gets an error:
     tid-reuse: /bd/home/philippe/gdb/git/build_moreaa/gdb/testsuite/../../../moreaa/gdb/testsuite/gdb.threads/tid-reuse.c:58: spawner_thread_func: Assertion `rc == 0' failed.

which causes a SIGABRT to be trapped by gdb, and tid-reuse does not reach the
after_count breakpoint:
  Thread 2 "tid-reuse" received signal SIGABRT, Aborted.
  [Switching to Thread 0x7ffff7518700 (LWP 10368)]
  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
  51	../sysdeps/unix/sysv/linux/raise.c: No such file or directory.
  (gdb) FAIL: gdb.threads/tid-reuse.exp: continue to breakpoint: after_count

After that, tid-reuse.exp gets the value of reuse_time, but this one kept its
initial value of -1 (as unsigned) :
  print reuse_time
  $1 = 4294967295
  (gdb) PASS: gdb.threads/tid-reuse.exp: get reuse_time

tid-reuse then dies, and the .exp script continues (with some FAIL)
till it executes:
  set timeout [expr $reuse_time * 2]

leading to the error:

  (gdb) ERROR: integer value too large to represent as non-long integer
      while executing
  "expect {
  -i exp8 -timeout 8589934590
          -re ".*A problem internal to GDB has been detected" {
              fail "$message (GDB internal error)"
              gdb_intern..."
      ("uplevel" body line 1)
      invoked from within
  "uplevel $body" ARITH IOVERFLOW {integer value too large to represent as non-long integer} integer value too large to represent as non-long integer
  ERROR: GDB process no longer exists

and then everything blocks.
This last 'GDB process no longer exists' is strange, as I still see the gdb
when this all blocks, e.g.
philippe 16058 31085  0 20:30 pts/15   00:00:00                         /bin/bash -c rootme=`pwd`; export rootme; srcdir=../../../binutils-gdb/gdb/testsuite ; export srcdir ; EXPECT=`if [
philippe 16386 16058  0 20:30 pts/15   00:00:00                           expect -- /usr/share/dejagnu/runtest.exp --status GDB_PARALLEL=yes --outdir=outputs/gdb.threads/tid-reuse gdb.thre
philippe 24848 16386  0 20:30 pts/20   00:00:00                             /bd/home/philippe/gdb/git/build_binutils-gdb/gdb/testsuite/../../gdb/gdb -nw -nx -data-directory /bd/home/philip

This patch gives a default value of 60, so that if ever something wrong happens
in tid-reuse, then the value retrieved by the .exp script stays in a reasonable
range.

Simon verified the patch by:
"I replaced the pthread_create call with the value 1 to simulate a
failure, and the test succeeds to fail quickly with your patch applied.
Without your patch, I get the infinite hang that you describe."

Compared to V1:
As suggested by Pedro, this version checks the pthread calls return
code (in particular of pthread_create) and reports the failure reason,
instead of just aborting.

gdb/testsuite/ChangeLog

2018-12-09  Philippe Waroquiers  <philippe.waroquiers@skynet.be>

	* gdb.threads/tid-reuse.c (REUSE_TIME_CAP): Declare as 60.
	(reuse_time): Initialize to REUSE_TIME_CAP.
	(check_rc): New function.
	(main): Use REUSE_TIME_CAP instead of hardcoded 60.
	Check pthread_create rc.
	(spawner_thread_func): Check pthread_create and pthread_join rc.