Re: [PATCH] tools/kvm_stat: fix termination behavior when not on a terminal

[Juergen Gross <jgross@suse.com>]

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Below patch was Acked in August last year, and despite a ping by me
in October it wasn't committed yet.

Pablo, do you have any concerns with this patch? Or are you just
no longer interested in maintaining kvm_stat?

As this patch is fixing a real bug which we at SUSE would like to
see fixed, please take the patch or tell us what to do to get it
upstream.

In case you just don't mind, I could offer to merge it via the Xen
tree, even if this patch doesn't really belong there.


Juergen

On 07.08.24 19:23, Claudio Fontana wrote:
> For the -l and -L options (logging mode), replace the use of the
> KeyboardInterrupt exception to gracefully terminate in favor
> of handling the SIGINT and SIGTERM signals.
> 
> This allows the program to be run from scripts and still be
> signaled to gracefully terminate without an interactive terminal.
> 
> Before this change, something like this script:
> 
> kvm_stat -p 85896 -d -t -s 1 -c -L kvm_stat_85896.csv &
> sleep 10
> pkill -TERM -P $$
> 
> would yield an empty log:
> -rw-r--r-- 1 root root     0 Aug  7 16:17 kvm_stat_85896.csv
> 
> after this commit:
> -rw-r--r-- 1 root root 13466 Aug  7 16:57 kvm_stat_85896.csv
> 
> Signed-off-by: Claudio Fontana <cfontana@suse.de>
> Cc: Dario Faggioli <dfaggioli@suse.com>
> Cc: Fabiano Rosas <farosas@suse.de>
> ---
>   tools/kvm/kvm_stat/kvm_stat     | 64 ++++++++++++++++-----------------
>   tools/kvm/kvm_stat/kvm_stat.txt | 12 +++++++
>   2 files changed, 44 insertions(+), 32 deletions(-)
> 
> diff --git a/tools/kvm/kvm_stat/kvm_stat b/tools/kvm/kvm_stat/kvm_stat
> index 15bf00e79e3f..2cf2da3ed002 100755
> --- a/tools/kvm/kvm_stat/kvm_stat
> +++ b/tools/kvm/kvm_stat/kvm_stat
> @@ -297,8 +297,6 @@ IOCTL_NUMBERS = {
>       'RESET':       0x00002403,
>   }
>   
> -signal_received = False
> -
>   ENCODING = locale.getpreferredencoding(False)
>   TRACE_FILTER = re.compile(r'^[^\(]*$')
>   
> @@ -1598,7 +1596,19 @@ class CSVFormat(object):
>   
>   def log(stats, opts, frmt, keys):
>       """Prints statistics as reiterating key block, multiple value blocks."""
> -    global signal_received
> +    signal_received = defaultdict(bool)
> +
> +    def handle_signal(sig, frame):
> +        nonlocal signal_received
> +        signal_received[sig] = True
> +        return
> +
> +
> +    signal.signal(signal.SIGINT, handle_signal)
> +    signal.signal(signal.SIGTERM, handle_signal)
> +    if opts.log_to_file:
> +        signal.signal(signal.SIGHUP, handle_signal)
> +
>       line = 0
>       banner_repeat = 20
>       f = None
> @@ -1624,39 +1634,31 @@ def log(stats, opts, frmt, keys):
>       do_banner(opts)
>       banner_printed = True
>       while True:
> -        try:
> -            time.sleep(opts.set_delay)
> -            if signal_received:
> -                banner_printed = True
> -                line = 0
> -                f.close()
> -                do_banner(opts)
> -                signal_received = False
> -            if (line % banner_repeat == 0 and not banner_printed and
> -                not (opts.log_to_file and isinstance(frmt, CSVFormat))):
> -                do_banner(opts)
> -                banner_printed = True
> -            values = stats.get()
> -            if (not opts.skip_zero_records or
> -                any(values[k].delta != 0 for k in keys)):
> -                do_statline(opts, values)
> -                line += 1
> -                banner_printed = False
> -        except KeyboardInterrupt:
> +        time.sleep(opts.set_delay)
> +        # Do not use the KeyboardInterrupt exception, because we may be running without a terminal
> +        if (signal_received[signal.SIGINT] or signal_received[signal.SIGTERM]):
>               break
> +        if signal_received[signal.SIGHUP]:
> +            banner_printed = True
> +            line = 0
> +            f.close()
> +            do_banner(opts)
> +            signal_received[signal.SIGHUP] = False
> +        if (line % banner_repeat == 0 and not banner_printed and
> +            not (opts.log_to_file and isinstance(frmt, CSVFormat))):
> +            do_banner(opts)
> +            banner_printed = True
> +        values = stats.get()
> +        if (not opts.skip_zero_records or
> +            any(values[k].delta != 0 for k in keys)):
> +            do_statline(opts, values)
> +            line += 1
> +            banner_printed = False
>   
>       if opts.log_to_file:
>           f.close()
>   
>   
> -def handle_signal(sig, frame):
> -    global signal_received
> -
> -    signal_received = True
> -
> -    return
> -
> -
>   def is_delay_valid(delay):
>       """Verify delay is in valid value range."""
>       msg = None
> @@ -1869,8 +1871,6 @@ def main():
>           sys.exit(0)
>   
>       if options.log or options.log_to_file:
> -        if options.log_to_file:
> -            signal.signal(signal.SIGHUP, handle_signal)
>           keys = sorted(stats.get().keys())
>           if options.csv:
>               frmt = CSVFormat(keys)
> diff --git a/tools/kvm/kvm_stat/kvm_stat.txt b/tools/kvm/kvm_stat/kvm_stat.txt
> index 3a9f2037bd23..4a99a111a93c 100644
> --- a/tools/kvm/kvm_stat/kvm_stat.txt
> +++ b/tools/kvm/kvm_stat/kvm_stat.txt
> @@ -115,6 +115,18 @@ OPTIONS
>   --skip-zero-records::
>           omit records with all zeros in logging mode
>   
> +
> +SIGNALS
> +-------
> +when kvm_stat is running in logging mode (either with -l or with -L),
> +it handles the following signals:
> +
> +SIGHUP - closes and reopens the log file (-L only), then continues.
> +
> +SIGINT - closes the log file and terminates.
> +SIGTERM - closes the log file and terminates.
> +
> +
>   SEE ALSO
>   --------
>   'perf'(1), 'trace-cmd'(1)


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