55 lines
2.1 KiB
Diff
55 lines
2.1 KiB
Diff
From ecbf46993f6ffbdc255f6ded3c6c05a8266a71e8 Mon Sep 17 00:00:00 2001
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From: David Mitchell <davem@iabyn.com>
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Date: Tue, 7 Aug 2018 12:26:31 +0100
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Subject: [PATCH] Time-HiRes/t/itimer.t: avoid race condition.
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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This test script sets a repeating interval timer going, and after 4
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'ticks' (SIGVTALRM), disables the timer (by setting it to zero).
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The main loop which does CPU burning, does a getitmer() every now and
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again, and when the value is zero, assumes the signal handler has
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disabled the timer, and so finishes.
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The trouble was that it was checking the 'time left', which can reach
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zero because the interval timer has counted down to zero, and the signal
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handler is about to be called, but the interval hasn't been reset back
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to 0.4s yet.
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i.e. the code doesn't distinguish between "timer disabled" and "timer
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just reached zero".
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In that scenario, the cleanup code in the test script disables the
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SIGVTALRM handler while the timer is still active, and so the process
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gets killed if another signal is raised.
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This commit changes the test to check the second value returned by
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getitmer() for being zero rather than the first - the second being the
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repeat interval, whichb is always 0.4 until the timer is disabled.
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Signed-off-by: Petr Písař <ppisar@redhat.com>
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---
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dist/Time-HiRes/t/itimer.t | 4 +++-
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1 file changed, 3 insertions(+), 1 deletion(-)
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diff --git a/dist/Time-HiRes/t/itimer.t b/dist/Time-HiRes/t/itimer.t
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index e196b1648c..432b224488 100644
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--- a/dist/Time-HiRes/t/itimer.t
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+++ b/dist/Time-HiRes/t/itimer.t
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@@ -51,7 +51,9 @@ ok(defined $virt && abs($virt / 0.5) - 1 < $limit,
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printf("# getitimer: %s\n", join(" ",
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Time::HiRes::getitimer(&Time::HiRes::ITIMER_VIRTUAL)));
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-while (Time::HiRes::getitimer(&Time::HiRes::ITIMER_VIRTUAL)) {
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+# burn CPU until the VTALRM signal handler sets the repeat interval to
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+# zero, indicating that the timer has fired 4 times.
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+while ((Time::HiRes::getitimer(&Time::HiRes::ITIMER_VIRTUAL))[1]) {
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my $j;
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for (1..1000) { $j++ } # Can't be unbreakable, must test getitimer().
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}
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--
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2.14.4
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