forked from luck/tmp_suning_uos_patched
99ee5315da
Some applications must be aware of clock realtime being set backward. A simple example is a clock applet which arms a timer for the next minute display. If clock realtime is set backward then the applet displays a stale time for the amount of time which the clock was set backwards. Due to that applications poll the time because we don't have an interface. Extend the timerfd interface by adding a flag which puts the timer onto a different internal realtime clock. All timers on this clock are expired whenever the clock was set. The timerfd core records the monotonic offset when the timer is created. When the timer is armed, then the current offset is compared to the previous recorded offset. When it has changed, then timerfd_settime returns -ECANCELED. When a timer is read the offset is compared and if it changed -ECANCELED returned to user space. Periodic timers are not rearmed in the cancelation case. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: John Stultz <johnstul@us.ibm.com> Cc: Chris Friesen <chris.friesen@genband.com> Tested-by: Kay Sievers <kay.sievers@vrfy.org> Cc: "Kirill A. Shutemov" <kirill@shutemov.name> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Davide Libenzi <davidel@xmailserver.org> Reviewed-by: Alexander Shishkin <virtuoso@slind.org> Link: http://lkml.kernel.org/r/%3Calpine.LFD.2.02.1104271359580.3323%40ionos%3E Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
33 lines
904 B
C
33 lines
904 B
C
/*
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* include/linux/timerfd.h
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*
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* Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
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*
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*/
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#ifndef _LINUX_TIMERFD_H
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#define _LINUX_TIMERFD_H
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/* For O_CLOEXEC and O_NONBLOCK */
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#include <linux/fcntl.h>
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/*
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* CAREFUL: Check include/asm-generic/fcntl.h when defining
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* new flags, since they might collide with O_* ones. We want
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* to re-use O_* flags that couldn't possibly have a meaning
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* from eventfd, in order to leave a free define-space for
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* shared O_* flags.
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*/
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#define TFD_TIMER_ABSTIME (1 << 0)
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#define TFD_TIMER_CANCELON_SET (1 << 1)
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#define TFD_CLOEXEC O_CLOEXEC
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#define TFD_NONBLOCK O_NONBLOCK
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#define TFD_SHARED_FCNTL_FLAGS (TFD_CLOEXEC | TFD_NONBLOCK)
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/* Flags for timerfd_create. */
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#define TFD_CREATE_FLAGS TFD_SHARED_FCNTL_FLAGS
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/* Flags for timerfd_settime. */
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#define TFD_SETTIME_FLAGS (TFD_TIMER_ABSTIME | TFD_TIMER_CANCELON_SET)
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#endif /* _LINUX_TIMERFD_H */
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