PING^2 Re: [RFA] Fix tid-reuse sometimes blocks for a very long (infinite?) time.

[Philippe Waroquiers <philippe dot waroquiers at skynet dot be>]

On Sat, 2018-11-24 at 13:58 +0100, Philippe Waroquiers wrote:
> Thanks
> Philippe
> 
> On Sun, 2018-11-04 at 21:00 +0100, Philippe Waroquiers wrote:
> > 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.
> > Note that I could not reproduce this failure often enough to be sure that
> > initializing to 60 ensures it does not block, but in any case, it should
> > not harm.
> > 
> > gdb/testsuite/ChangeLog
> > 
> > 2018-11-04  Philippe Waroquiers  <philippe.waroquiers@skynet.be>
> > 
> > 	* gdb.threads/tid-reuse.c (REUSE_TIME_CAP): Declare as 60.
> > 	(reuse_time): Initialize to REUSE_TIME_CAP.
> > 	(main): Use REUSE_TIME_CAP instead of hardcoded 60.
> > ---
> >  gdb/testsuite/gdb.threads/tid-reuse.c | 11 +++++++----
> >  1 file changed, 7 insertions(+), 4 deletions(-)
> > 
> > diff --git a/gdb/testsuite/gdb.threads/tid-reuse.c b/gdb/testsuite/gdb.threads/tid-reuse.c
> > index 1741325a5b..0cdd580441 100644
> > --- a/gdb/testsuite/gdb.threads/tid-reuse.c
> > +++ b/gdb/testsuite/gdb.threads/tid-reuse.c
> > @@ -34,8 +34,11 @@ unsigned long thread_counter;
> >     incremented, this is enough for the tid numbers to wrap around.  On
> >     targets that randomize thread IDs, this is enough time to give each
> >     number in the thread number space some chance of reuse.  It'll be
> > -   capped to a lower value if we can't compute it.  */
> > -unsigned int reuse_time = -1;
> > +   capped to a lower value if we can't compute it.  REUSE_TIME_CAP
> > +   is the max value, and the default value if ever the program
> > +   has problem to compute it.  */
> > +#define REUSE_TIME_CAP 60
> > +unsigned int reuse_time = REUSE_TIME_CAP;
> >  
> >  void *
> >  do_nothing_thread_func (void *arg)
> > @@ -138,8 +141,8 @@ main (int argc, char *argv[])
> >       pid_max=32768.  Going forward, as machines get faster, this will
> >       need less time, unless pid_max is set to a very high number.  To
> >       avoid unreasonably long test time, cap to an upper bound.  */
> > -  if (reuse_time > 60)
> > -    reuse_time = 60;
> > +  if (reuse_time > REUSE_TIME_CAP)
> > +    reuse_time = REUSE_TIME_CAP;
> >    printf ("thread_counter=%lu, tid_max = %ld, reuse_time_raw=%u, reuse_time=%u\n",
> >  	  thread_counter, tid_max, reuse_time_raw, reuse_time);
> >    after_count ();