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beaa447a29
In a few places in libvirt we busy-wait for events, for example qemu creating a monitor socket. This is problematic because: - We need to choose a sufficiently small polling period so that libvirt doesn't add unnecessary delays. - We need to choose a sufficiently large polling period so that the effect of busy-waiting doesn't affect the system. The solution to this conflict is to use an exponential backoff. This patch adds two functions to hide the details, and modifies a few places where we currently busy-wait. Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
79 lines
2.5 KiB
C
79 lines
2.5 KiB
C
/*
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* virtime.h: Time handling functions
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*
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* Copyright (C) 2006-2011, 2014 Red Hat, Inc.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library. If not, see
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* <http://www.gnu.org/licenses/>.
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*
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* Author: Daniel P. Berrange <berrange@redhat.com>
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*/
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#ifndef __VIR_TIME_H__
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# define __VIR_TIME_H__
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# include <time.h>
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# include "internal.h"
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/* The format string we intend to use is:
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*
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* Yr Mon Day Hour Min Sec Ms TZ
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* %4d-%02d-%02d %02d:%02d:%02d.%03d+0000
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*
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*/
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# define VIR_TIME_STRING_BUFLEN \
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(4 + 1 + 2 + 1 + 2 + 1 + 2 + 1 + 2 + 1 + 2 + 1 + 3 + 5 + 1)
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/* Yr Mon Day Hour Min Sec Ms TZ NULL */
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void virTimeFieldsThen(unsigned long long when, struct tm *fields)
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ATTRIBUTE_NONNULL(2);
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/* These APIs are async signal safe and return -1, setting
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* errno on failure */
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int virTimeMillisNowRaw(unsigned long long *now)
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ATTRIBUTE_NONNULL(1) ATTRIBUTE_RETURN_CHECK;
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int virTimeFieldsNowRaw(struct tm *fields)
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ATTRIBUTE_NONNULL(1) ATTRIBUTE_RETURN_CHECK;
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int virTimeStringNowRaw(char *buf)
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ATTRIBUTE_NONNULL(1) ATTRIBUTE_RETURN_CHECK;
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int virTimeStringThenRaw(unsigned long long when, char *buf)
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ATTRIBUTE_NONNULL(2) ATTRIBUTE_RETURN_CHECK;
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/* These APIs are *not* async signal safe and return -1,
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* raising a libvirt error on failure
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*/
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int virTimeMillisNow(unsigned long long *now)
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ATTRIBUTE_NONNULL(1) ATTRIBUTE_RETURN_CHECK;
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int virTimeFieldsNow(struct tm *fields)
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ATTRIBUTE_NONNULL(1) ATTRIBUTE_RETURN_CHECK;
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char *virTimeStringNow(void);
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char *virTimeStringThen(unsigned long long when);
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int virTimeLocalOffsetFromUTC(long *offset)
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ATTRIBUTE_NONNULL(1) ATTRIBUTE_RETURN_CHECK;
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typedef struct {
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unsigned long long start_t;
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unsigned long long next;
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unsigned long long limit_t;
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} virTimeBackOffVar;
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int virTimeBackOffStart(virTimeBackOffVar *var,
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unsigned long long first, unsigned long long timeout);
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bool virTimeBackOffWait(virTimeBackOffVar *var);
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#endif
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