Re: [PATCH v3 3/3] selftests/tracing: Add hist poll() support test

[Masami Hiramatsu (Google) <mhiramat@kernel.org>]

On Wed, 14 Aug 2024 05:38:24 -0600
Shuah Khan <skhan@linuxfoundation.org> wrote:

> On 8/13/24 18:11, Masami Hiramatsu (Google) wrote:
> > From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> > 
> > Add a testcase for poll() on hist file. This introduces a helper binary
> > to the ftracetest, because there is no good way to reliably execute
> > poll() on hist file.
> > 
> > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> > ---
> >   Changes in v2:
> >    - Update poll command to support both of POLLIN and POLLPRI, and timeout.
> >    - Identify unsupported stable kernel if poll-in returns soon.
> >    - Test both of POLLIN and POLLPRI.
> > ---
> >   tools/testing/selftests/ftrace/Makefile            |    2 +
> >   tools/testing/selftests/ftrace/poll.c              |   62 +++++++++++++++++
> >   .../ftrace/test.d/trigger/trigger-hist-poll.tc     |   74 ++++++++++++++++++++
> >   3 files changed, 138 insertions(+)
> >   create mode 100644 tools/testing/selftests/ftrace/poll.c
> >   create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-poll.tc
> > 
> > diff --git a/tools/testing/selftests/ftrace/Makefile b/tools/testing/selftests/ftrace/Makefile
> > index a1e955d2de4c..49d96bb16355 100644
> > --- a/tools/testing/selftests/ftrace/Makefile
> > +++ b/tools/testing/selftests/ftrace/Makefile
> > @@ -6,4 +6,6 @@ TEST_PROGS := ftracetest-ktap
> >   TEST_FILES := test.d settings
> >   EXTRA_CLEAN := $(OUTPUT)/logs/*
> >   
> > +TEST_GEN_PROGS = poll
> > +
> >   include ../lib.mk
> > diff --git a/tools/testing/selftests/ftrace/poll.c b/tools/testing/selftests/ftrace/poll.c
> > new file mode 100644
> > index 000000000000..8003a59fe042
> > --- /dev/null
> > +++ b/tools/testing/selftests/ftrace/poll.c
> > @@ -0,0 +1,62 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Simple poll on a file.
> > + *
> > + * Copyright (c) 2024 Google LLC.
> > + */
> > +
> > +#include <errno.h>
> > +#include <fcntl.h>
> > +#include <poll.h>
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <string.h>
> > +#include <unistd.h>
> > +
> > +#define BUFSIZE 4096
> > +
> > +/*
> > + * Usage:
> > + *  poll <in|pri> <FILE> [timeout]
> > + */
> > +int main(int argc, char *argv[])
> > +{
> > +	struct pollfd pfd;
> > +	char buf[BUFSIZE];
> > +	int timeout = -1;
> > +	int ret;
> > +
> > +	if (argc < 3)
> > +		return -1;
> > +
> > +	if (!strcmp(argv[1], "in"))
> > +		pfd.events = POLLIN;
> > +	else if (!strcmp(argv[1], "pri"))
> > +		pfd.events = POLLPRI;
> > +
> > +	pfd.fd = open(argv[2], O_RDONLY);
> > +	if (pfd.fd < 0) {
> > +		perror("open");
> > +		return -1;
> > +	}
> > +
> > +	if (argc == 4)
> > +		timeout = atoi(argv[3]);
> 
> This code can be simpler and more maintainable using getopt.
> Any reason why you didn't use it?

There is no reason. OK, let me use getopt to clean it up.

> 
> > +
> > +	/* Reset poll by read if POLLIN is specified. */
> > +	if (pfd.events & POLLIN)
> > +		do {} while (read(pfd.fd, buf, BUFSIZE) == BUFSIZE);
> > +
> > +	ret = poll(&pfd, 1, timeout);
> > +	if (ret < 0 && errno != EINTR) {
> > +		perror("poll")> +		return -1;
> > +	}
> > +	close(pfd.fd);
> > +
> > +	/* If timeout happned, return code is 0 */
> 
> Spelling - happened

Oops, thanks!

> 
> > +	if (ret == 0)
> > +		return 1;
> > +
> > +	return 0;
> > +}
> > diff --git a/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-poll.tc b/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-poll.tc
> > new file mode 100644
> > index 000000000000..53bea74e2234
> > --- /dev/null
> > +++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-poll.tc
> > @@ -0,0 +1,74 @@
> > +#!/bin/sh
> > +# SPDX-License-Identifier: GPL-2.0
> > +# description: event trigger - test poll wait on histogram
> > +# requires: set_event events/sched/sched_process_free/trigger events/sched/sched_process_free/hist
> > +# flags: instance
> > +
> > +POLL=${FTRACETEST_ROOT}/poll
> > +
> > +if [ ! -x ${POLL} ]; then
> > +  echo "poll program is not compiled!"
> > +  exit_unresolved
> > +fi
> > +
> > +EVENT=events/sched/sched_process_free/
> > +
> > +# Check poll ops is supported. Before implementing poll on hist file, it
> > +# returns soon with POLLIN | POLLOUT, but not POLLPRI.
> > +
> > +# This must wait >1 sec and return 1 (timeout).
> > +set +e
> > +${POLL} in ${EVENT}/hist 1000
> > +ret=$?
> > +set -e
> > +if [ ${ret} != 1 ]; then
> > +  echo "poll on hist file is not supported"
> > +  exit_unsupported
> > +fi
> > +
> > +# Test POLLIN
> > +echo > trace
> > +echo "hist:key=comm" > ${EVENT}/trigger
> > +echo 1 > ${EVENT}/enable
> > +
> > +# This sleep command will exit after 2 seconds.
> > +sleep 2 &
> > +BGPID=$!
> > +# if timeout happens, poll returns 1.
> > +${POLL} in ${EVENT}/hist 4000
> > +echo 0 > tracing_on
> > +
> > +if [ -d /proc/${BGPID} ]; then
> > +  echo "poll exits too soon"
> > +  kill -KILL ${BGPID} ||:
> > +  exit_fail
> > +fi
> > +
> > +if ! grep -qw "sleep" trace; then
> > +  echo "poll exits before event happens"
> > +  exit_fail
> > +fi
> > +
> > +# Test POLLPRI
> > +echo > trace
> > +echo 1 > tracing_on
> > +
> > +# This sleep command will exit after 2 seconds.
> > +sleep 2 &
> > +BGPID=$!
> > +# if timeout happens, poll returns 1.
> > +${POLL} pri ${EVENT}/hist 4000
> > +echo 0 > tracing_on
> > +
> > +if [ -d /proc/${BGPID} ]; then
> > +  echo "poll exits too soon"
> > +  kill -KILL ${BGPID} ||:
> > +  exit_fail
> > +fi
> > +
> > +if ! grep -qw "sleep" trace; then
> > +  echo "poll exits before event happens"
> > +  exit_fail
> > +fi
> > +
> > +exit_pass
> > 
> 
> thanks,
> -- Shuah
> 


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>