[DTrace-devel] [PATCH v2] test: Wait for output to flush out in enable_pid

[Kris Van Hees]

On Wed, Jul 30, 2025 at 10:18:17AM -0400, Kris Van Hees via DTrace-devel wrote:
> I still see intermittent FAILs.  I wonder whether there is a potentially unsafe
> contruct at work (see below).

Hm, no that does not fix it either.

Eugene - can you have a closer look at this and see what might be going on?

> On Sat, Jun 28, 2025 at 06:30:50PM -0400, eugene.loh at oracle.com wrote:
> > From: Eugene Loh <eugene.loh at oracle.com>
> > 
> > Our luck with this test has been quite good, but it sometimes fails
> > to show its last lines of output.  That is, we send a USR1 to the
> > trigger processes to set off the final output and we immediately
> > cat the output files.  If there is any delay in handling the signal,
> > the last output will be missing.
> > 
> > Have the processes terminate themselves when their last output is
> > flushed; then wait for those processes.  Also, skip testing altogether if
> > there is only a single processor to run the two, hard-spinning processes.
> > 
> > Signed-off-by: Eugene Loh <eugene.loh at oracle.com>
> > ---
> >  test/unittest/usdt/tst.enable_pid.sh | 17 ++++++++++++-----
> >  test/unittest/usdt/tst.enable_pid.x  |  8 ++++++++
> >  2 files changed, 20 insertions(+), 5 deletions(-)
> >  create mode 100755 test/unittest/usdt/tst.enable_pid.x
> > 
> > diff --git a/test/unittest/usdt/tst.enable_pid.sh b/test/unittest/usdt/tst.enable_pid.sh
> > index 7f4f68698..296cfb382 100755
> > --- a/test/unittest/usdt/tst.enable_pid.sh
> > +++ b/test/unittest/usdt/tst.enable_pid.sh
> > @@ -33,6 +33,8 @@ EOF
> >  cat > main.c <<EOF
> >  #include <signal.h>
> >  #include <stdio.h>
> > +#include <stdlib.h>
> > +#include <string.h>
> >  #include "prov.h"
> >  
> >  /* We check if the is-enabled probe is or is not enabled (or unknown). */
> > @@ -41,7 +43,7 @@ cat > main.c <<EOF
> >  #define ENABLED_UNK	3
> >  
> >  /* Start with the previous probe "unknown". */
> > -int prv = ENABLED_UNK;
> > +int prv = ENABLED_UNK, nepochs_left = 4;
> >  long long num = 0;
> >  
> >  /* Report how many times the previous case was encountered. */
> > @@ -71,6 +73,9 @@ static void mark_epoch(int sig) {
> >  	report();
> >  	printf("=== epoch ===\n");
> >  	fflush(stdout);
> > +	nepochs_left--;
> > +	if (nepochs_left <= 0)
> > +		exit(0);
> 
> I wonder whether this could still cause some output to get lost.  I would
> actually move the conditional and exit to the end of the loop in main(),
> so that we check nepochs_left and exit when <= 0 outside of the interrupt
> handler.
> 
> I am running a long sequence of this test to see if that helps/fixes it.
> 
> >  }
> >  
> >  int
> > @@ -79,7 +84,7 @@ main(int argc, char **argv)
> >  	struct sigaction act;
> >  
> >  	/* Set USR1 to mark epochs. */
> > -	act.sa_flags = 0;
> > +	memset(&act, 0, sizeof(act));
> >  	act.sa_handler = mark_epoch;
> >  	if (sigaction(SIGUSR1, &act, NULL)) {
> >  		printf("set handler failed\n");
> > @@ -172,13 +177,15 @@ for pid in 1 $pid1 $pid2 '*'; do
> >  	kill -USR1 $pid2
> >  done
> >  
> > +# Wait for the processes.
> > +wait $pid1
> > +wait $pid2
> > +
> > +# Dump the output.
> >  echo done
> >  echo "========== out 1"; cat out.1
> >  echo "========== out 2"; cat out.2
> >  
> >  echo success
> >  
> > -kill -TERM $pid1
> > -kill -TERM $pid2
> > -
> >  exit 0
> > diff --git a/test/unittest/usdt/tst.enable_pid.x b/test/unittest/usdt/tst.enable_pid.x
> > new file mode 100755
> > index 000000000..9506674ee
> > --- /dev/null
> > +++ b/test/unittest/usdt/tst.enable_pid.x
> > @@ -0,0 +1,8 @@
> > +#!/bin/sh
> > +
> > +if [ `grep -c ^processor /proc/cpuinfo` -lt 2 ]; then
> > +	echo test should have at least two processors
> > +	exit 2
> > +fi
> > +
> > +exit 0
> > -- 
> > 2.43.5
> > 
> 
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