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5442e9fbd7
The read() of timerfd files allows to fetch the number of timer ticks while there is no way to set it back from userspace. To restore the timer's state as it was at checkpoint moment we need a path to bring @ticks back. Initially I thought about writing ticks back via write() interface but it seems such API is somehow obscure. Instead implement timerfd_ioctl() method with TFD_IOC_SET_TICKS command which allows to adjust @ticks into non-zero value waking up the waiters. I wrapped code with CONFIG_CHECKPOINT_RESTORE which can be dropped off if there users except c/r camp appear. v2 (by akpm@): - Use define timerfd_ioctl NULL for non c/r config v3: - Use copy_from_user for @ticks fetching since not all arch support get_user for 8 byte argument Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Andrey Vagin <avagin@openvz.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Christopher Covington <cov@codeaurora.org> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Vladimir Davydov <vdavydov@parallels.com> Link: http://lkml.kernel.org/r/20140715215703.285617923@openvz.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
38 lines
999 B
C
38 lines
999 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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/* For _IO helpers */
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#include <linux/ioctl.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_CANCEL_ON_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_CANCEL_ON_SET)
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#define TFD_IOC_SET_TICKS _IOW('T', 0, u64)
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#endif /* _LINUX_TIMERFD_H */
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