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

Kris Van Hees
2025-07-30T14:26:58Z

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@oracle.com wrote:
> > From: Eugene Loh <eugene.loh@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@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
> >
>
> _______________________________________________
> DTrace-devel mailing list
> DTrace-devel@oss.oracle.com
> https://oss.oracle.com/mailman/listinfo/dtrace-devel