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linux/kernel/posix-timers.c

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/*
* linux/kernel/posix-timers.c
*
*
* 2002-10-15 Posix Clocks & timers
* by George Anzinger george@mvista.com
*
* Copyright (C) 2002 2003 by MontaVista Software.
*
* 2004-06-01 Fix CLOCK_REALTIME clock/timer TIMER_ABSTIME bug.
* Copyright (C) 2004 Boris Hu
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or (at
* your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
* MontaVista Software | 1237 East Arques Avenue | Sunnyvale | CA 94085 | USA
*/
/* These are all the functions necessary to implement
* POSIX clocks & timers
*/
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/time.h>
#include <linux/mutex.h>
#include <asm/uaccess.h>
#include <linux/list.h>
#include <linux/init.h>
#include <linux/compiler.h>
#include <linux/idr.h>
#include <linux/posix-clock.h>
#include <linux/posix-timers.h>
#include <linux/syscalls.h>
#include <linux/wait.h>
#include <linux/workqueue.h>
#include <linux/export.h>
/*
* Management arrays for POSIX timers. Timers are kept in slab memory
* Timer ids are allocated by an external routine that keeps track of the
* id and the timer. The external interface is:
*
* void *idr_find(struct idr *idp, int id); to find timer_id <id>
* int idr_get_new(struct idr *idp, void *ptr); to get a new id and
* related it to <ptr>
* void idr_remove(struct idr *idp, int id); to release <id>
* void idr_init(struct idr *idp); to initialize <idp>
* which we supply.
* The idr_get_new *may* call slab for more memory so it must not be
* called under a spin lock. Likewise idr_remore may release memory
* (but it may be ok to do this under a lock...).
* idr_find is just a memory look up and is quite fast. A -1 return
* indicates that the requested id does not exist.
*/
/*
* Lets keep our timers in a slab cache :-)
*/
static struct kmem_cache *posix_timers_cache;
static struct idr posix_timers_id;
static DEFINE_SPINLOCK(idr_lock);
/*
* we assume that the new SIGEV_THREAD_ID shares no bits with the other
* SIGEV values. Here we put out an error if this assumption fails.
*/
#if SIGEV_THREAD_ID != (SIGEV_THREAD_ID & \
~(SIGEV_SIGNAL | SIGEV_NONE | SIGEV_THREAD))
#error "SIGEV_THREAD_ID must not share bit with other SIGEV values!"
#endif
/*
* parisc wants ENOTSUP instead of EOPNOTSUPP
*/
#ifndef ENOTSUP
# define ENANOSLEEP_NOTSUP EOPNOTSUPP
#else
# define ENANOSLEEP_NOTSUP ENOTSUP
#endif
/*
* The timer ID is turned into a timer address by idr_find().
* Verifying a valid ID consists of:
*
* a) checking that idr_find() returns other than -1.
* b) checking that the timer id matches the one in the timer itself.
* c) that the timer owner is in the callers thread group.
*/
/*
* CLOCKs: The POSIX standard calls for a couple of clocks and allows us
* to implement others. This structure defines the various
* clocks.
*
* RESOLUTION: Clock resolution is used to round up timer and interval
* times, NOT to report clock times, which are reported with as
* much resolution as the system can muster. In some cases this
* resolution may depend on the underlying clock hardware and
* may not be quantifiable until run time, and only then is the
* necessary code is written. The standard says we should say
* something about this issue in the documentation...
*
* FUNCTIONS: The CLOCKs structure defines possible functions to
* handle various clock functions.
*
* The standard POSIX timer management code assumes the
* following: 1.) The k_itimer struct (sched.h) is used for
* the timer. 2.) The list, it_lock, it_clock, it_id and
* it_pid fields are not modified by timer code.
*
* Permissions: It is assumed that the clock_settime() function defined
* for each clock will take care of permission checks. Some
* clocks may be set able by any user (i.e. local process
* clocks) others not. Currently the only set able clock we
* have is CLOCK_REALTIME and its high res counter part, both of
* which we beg off on and pass to do_sys_settimeofday().
*/
static struct k_clock posix_clocks[MAX_CLOCKS];
/*
* These ones are defined below.
*/
static int common_nsleep(const clockid_t, int flags, struct timespec *t,
struct timespec __user *rmtp);
static int common_timer_create(struct k_itimer *new_timer);
static void common_timer_get(struct k_itimer *, struct itimerspec *);
static int common_timer_set(struct k_itimer *, int,
struct itimerspec *, struct itimerspec *);
static int common_timer_del(struct k_itimer *timer);
static enum hrtimer_restart posix_timer_fn(struct hrtimer *data);
static struct k_itimer *__lock_timer(timer_t timer_id, unsigned long *flags);
#define lock_timer(tid, flags) \
({ struct k_itimer *__timr; \
__cond_lock(&__timr->it_lock, __timr = __lock_timer(tid, flags)); \
__timr; \
})
static inline void unlock_timer(struct k_itimer *timr, unsigned long flags)
{
spin_unlock_irqrestore(&timr->it_lock, flags);
}
/* Get clock_realtime */
static int posix_clock_realtime_get(clockid_t which_clock, struct timespec *tp)
{
ktime_get_real_ts(tp);
return 0;
}
/* Set clock_realtime */
static int posix_clock_realtime_set(const clockid_t which_clock,
const struct timespec *tp)
{
return do_sys_settimeofday(tp, NULL);
}
static int posix_clock_realtime_adj(const clockid_t which_clock,
struct timex *t)
{
return do_adjtimex(t);
}
/*
* Get monotonic time for posix timers
*/
static int posix_ktime_get_ts(clockid_t which_clock, struct timespec *tp)
{
ktime_get_ts(tp);
return 0;
}
/*
* Get monotonic-raw time for posix timers
*/
static int posix_get_monotonic_raw(clockid_t which_clock, struct timespec *tp)
{
getrawmonotonic(tp);
return 0;
}
static int posix_get_realtime_coarse(clockid_t which_clock, struct timespec *tp)
{
*tp = current_kernel_time();
return 0;
}
static int posix_get_monotonic_coarse(clockid_t which_clock,
struct timespec *tp)
{
*tp = get_monotonic_coarse();
return 0;
}
static int posix_get_coarse_res(const clockid_t which_clock, struct timespec *tp)
{
*tp = ktime_to_timespec(KTIME_LOW_RES);
return 0;
}
static int posix_get_boottime(const clockid_t which_clock, struct timespec *tp)
{
get_monotonic_boottime(tp);
return 0;
}
/*
* Initialize everything, well, just everything in Posix clocks/timers ;)
*/
static __init int init_posix_timers(void)
{
struct k_clock clock_realtime = {
.clock_getres = hrtimer_get_res,
.clock_get = posix_clock_realtime_get,
.clock_set = posix_clock_realtime_set,
.clock_adj = posix_clock_realtime_adj,
.nsleep = common_nsleep,
.nsleep_restart = hrtimer_nanosleep_restart,
.timer_create = common_timer_create,
.timer_set = common_timer_set,
.timer_get = common_timer_get,
.timer_del = common_timer_del,
};
struct k_clock clock_monotonic = {
.clock_getres = hrtimer_get_res,
.clock_get = posix_ktime_get_ts,
.nsleep = common_nsleep,
.nsleep_restart = hrtimer_nanosleep_restart,
.timer_create = common_timer_create,
.timer_set = common_timer_set,
.timer_get = common_timer_get,
.timer_del = common_timer_del,
};
struct k_clock clock_monotonic_raw = {
.clock_getres = hrtimer_get_res,
.clock_get = posix_get_monotonic_raw,
};
struct k_clock clock_realtime_coarse = {
.clock_getres = posix_get_coarse_res,
.clock_get = posix_get_realtime_coarse,
};
struct k_clock clock_monotonic_coarse = {
.clock_getres = posix_get_coarse_res,
.clock_get = posix_get_monotonic_coarse,
};
struct k_clock clock_boottime = {
.clock_getres = hrtimer_get_res,
.clock_get = posix_get_boottime,
.nsleep = common_nsleep,
.nsleep_restart = hrtimer_nanosleep_restart,
.timer_create = common_timer_create,
.timer_set = common_timer_set,
.timer_get = common_timer_get,
.timer_del = common_timer_del,
};
posix_timers_register_clock(CLOCK_REALTIME, &clock_realtime);
posix_timers_register_clock(CLOCK_MONOTONIC, &clock_monotonic);
posix_timers_register_clock(CLOCK_MONOTONIC_RAW, &clock_monotonic_raw);
posix_timers_register_clock(CLOCK_REALTIME_COARSE, &clock_realtime_coarse);
posix_timers_register_clock(CLOCK_MONOTONIC_COARSE, &clock_monotonic_coarse);
posix_timers_register_clock(CLOCK_BOOTTIME, &clock_boottime);
posix_timers_cache = kmem_cache_create("posix_timers_cache",
sizeof (struct k_itimer), 0, SLAB_PANIC,
NULL);
idr_init(&posix_timers_id);
return 0;
}
__initcall(init_posix_timers);
static void schedule_next_timer(struct k_itimer *timr)
{
struct hrtimer *timer = &timr->it.real.timer;
if (timr->it.real.interval.tv64 == 0)
return;
timerfd: new timerfd API This is the new timerfd API as it is implemented by the following patch: int timerfd_create(int clockid, int flags); int timerfd_settime(int ufd, int flags, const struct itimerspec *utmr, struct itimerspec *otmr); int timerfd_gettime(int ufd, struct itimerspec *otmr); The timerfd_create() API creates an un-programmed timerfd fd. The "clockid" parameter can be either CLOCK_MONOTONIC or CLOCK_REALTIME. The timerfd_settime() API give new settings by the timerfd fd, by optionally retrieving the previous expiration time (in case the "otmr" parameter is not NULL). The time value specified in "utmr" is absolute, if the TFD_TIMER_ABSTIME bit is set in the "flags" parameter. Otherwise it's a relative time. The timerfd_gettime() API returns the next expiration time of the timer, or {0, 0} if the timerfd has not been set yet. Like the previous timerfd API implementation, read(2) and poll(2) are supported (with the same interface). Here's a simple test program I used to exercise the new timerfd APIs: http://www.xmailserver.org/timerfd-test2.c [akpm@linux-foundation.org: coding-style cleanups] [akpm@linux-foundation.org: fix ia64 build] [akpm@linux-foundation.org: fix m68k build] [akpm@linux-foundation.org: fix mips build] [akpm@linux-foundation.org: fix alpha, arm, blackfin, cris, m68k, s390, sparc and sparc64 builds] [heiko.carstens@de.ibm.com: fix s390] [akpm@linux-foundation.org: fix powerpc build] [akpm@linux-foundation.org: fix sparc64 more] Signed-off-by: Davide Libenzi <davidel@xmailserver.org> Cc: Michael Kerrisk <mtk-manpages@gmx.net> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Davide Libenzi <davidel@xmailserver.org> Cc: Michael Kerrisk <mtk-manpages@gmx.net> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Davide Libenzi <davidel@xmailserver.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 06:27:26 +00:00
timr->it_overrun += (unsigned int) hrtimer_forward(timer,
timer->base->get_time(),
timr->it.real.interval);
timr->it_overrun_last = timr->it_overrun;
timr->it_overrun = -1;
++timr->it_requeue_pending;
hrtimer_restart(timer);
}
/*
* This function is exported for use by the signal deliver code. It is
* called just prior to the info block being released and passes that
* block to us. It's function is to update the overrun entry AND to
* restart the timer. It should only be called if the timer is to be
* restarted (i.e. we have flagged this in the sys_private entry of the
* info block).
*
* To protect against the timer going away while the interrupt is queued,
* we require that the it_requeue_pending flag be set.
*/
void do_schedule_next_timer(struct siginfo *info)
{
struct k_itimer *timr;
unsigned long flags;
timr = lock_timer(info->si_tid, &flags);
if (timr && timr->it_requeue_pending == info->si_sys_private) {
if (timr->it_clock < 0)
posix_cpu_timer_schedule(timr);
else
schedule_next_timer(timr);
info->si_overrun += timr->it_overrun_last;
}
if (timr)
unlock_timer(timr, flags);
}
posix-timers: fix posix_timer_event() vs dequeue_signal() race The bug was reported and analysed by Mark McLoughlin <markmc@redhat.com>, the patch is based on his and Roland's suggestions. posix_timer_event() always rewrites the pre-allocated siginfo before sending the signal. Most of the written info is the same all the time, but memset(0) is very wrong. If ->sigq is queued we can race with collect_signal() which can fail to find this siginfo looking at .si_signo, or copy_siginfo() can copy the wrong .si_code/si_tid/etc. In short, sys_timer_settime() can in fact stop the active timer, or the user can receive the siginfo with the wrong .si_xxx values. Move "memset(->info, 0)" from posix_timer_event() to alloc_posix_timer(), change send_sigqueue() to set .si_overrun = 0 when ->sigq is not queued. It would be nice to move the whole sigq->info initialization from send to create path, but this is not easy to do without uglifying timer_create() further. As Roland rightly pointed out, we need more cleanups/fixes here, see the "FIXME" comment in the patch. Hopefully this patch makes sense anyway, and it can mask the most bad implications. Reported-by: Mark McLoughlin <markmc@redhat.com> Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Cc: Mark McLoughlin <markmc@redhat.com> Cc: Oliver Pinter <oliver.pntr@gmail.com> Cc: Roland McGrath <roland@redhat.com> Cc: stable@kernel.org Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> kernel/posix-timers.c | 17 +++++++++++++---- kernel/signal.c | 1 + 2 files changed, 14 insertions(+), 4 deletions(-)
2008-07-23 16:52:05 +00:00
int posix_timer_event(struct k_itimer *timr, int si_private)
{
struct task_struct *task;
int shared, ret = -1;
posix-timers: fix posix_timer_event() vs dequeue_signal() race The bug was reported and analysed by Mark McLoughlin <markmc@redhat.com>, the patch is based on his and Roland's suggestions. posix_timer_event() always rewrites the pre-allocated siginfo before sending the signal. Most of the written info is the same all the time, but memset(0) is very wrong. If ->sigq is queued we can race with collect_signal() which can fail to find this siginfo looking at .si_signo, or copy_siginfo() can copy the wrong .si_code/si_tid/etc. In short, sys_timer_settime() can in fact stop the active timer, or the user can receive the siginfo with the wrong .si_xxx values. Move "memset(->info, 0)" from posix_timer_event() to alloc_posix_timer(), change send_sigqueue() to set .si_overrun = 0 when ->sigq is not queued. It would be nice to move the whole sigq->info initialization from send to create path, but this is not easy to do without uglifying timer_create() further. As Roland rightly pointed out, we need more cleanups/fixes here, see the "FIXME" comment in the patch. Hopefully this patch makes sense anyway, and it can mask the most bad implications. Reported-by: Mark McLoughlin <markmc@redhat.com> Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Cc: Mark McLoughlin <markmc@redhat.com> Cc: Oliver Pinter <oliver.pntr@gmail.com> Cc: Roland McGrath <roland@redhat.com> Cc: stable@kernel.org Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> kernel/posix-timers.c | 17 +++++++++++++---- kernel/signal.c | 1 + 2 files changed, 14 insertions(+), 4 deletions(-)
2008-07-23 16:52:05 +00:00
/*
* FIXME: if ->sigq is queued we can race with
* dequeue_signal()->do_schedule_next_timer().
*
* If dequeue_signal() sees the "right" value of
* si_sys_private it calls do_schedule_next_timer().
* We re-queue ->sigq and drop ->it_lock().
* do_schedule_next_timer() locks the timer
* and re-schedules it while ->sigq is pending.
* Not really bad, but not that we want.
*/
timr->sigq->info.si_sys_private = si_private;
rcu_read_lock();
task = pid_task(timr->it_pid, PIDTYPE_PID);
if (task) {
shared = !(timr->it_sigev_notify & SIGEV_THREAD_ID);
ret = send_sigqueue(timr->sigq, task, shared);
}
rcu_read_unlock();
/* If we failed to send the signal the timer stops. */
return ret > 0;
}
EXPORT_SYMBOL_GPL(posix_timer_event);
/*
* This function gets called when a POSIX.1b interval timer expires. It
* is used as a callback from the kernel internal timer. The
* run_timer_list code ALWAYS calls with interrupts on.
* This code is for CLOCK_REALTIME* and CLOCK_MONOTONIC* timers.
*/
static enum hrtimer_restart posix_timer_fn(struct hrtimer *timer)
{
struct k_itimer *timr;
unsigned long flags;
int si_private = 0;
enum hrtimer_restart ret = HRTIMER_NORESTART;
timr = container_of(timer, struct k_itimer, it.real.timer);
spin_lock_irqsave(&timr->it_lock, flags);
if (timr->it.real.interval.tv64 != 0)
si_private = ++timr->it_requeue_pending;
if (posix_timer_event(timr, si_private)) {
/*
* signal was not sent because of sig_ignor
* we will not get a call back to restart it AND
* it should be restarted.
*/
if (timr->it.real.interval.tv64 != 0) {
posix-timers: Prevent softirq starvation by small intervals and SIG_IGN posix-timers which deliver an ignored signal are currently rearmed in the timer softirq: This is necessary because the timer needs to be delivered again when SIG_IGN is removed. This is not a problem, when the interval is reasonable. With high resolution timers enabled one might arm a posix timer with a very small interval and ignore the signal. This might lead to a softirq starvation when the interval is so small that the timer is requeued onto the softirq pending list right away. This problem was pointed out by Jan Kiszka. Thanks Jan ! The correct solution would be to stop the timer, when the signal is ignored and rearm it when SIG_IGN is removed. Unfortunately this requires modification in sigaction and involves non trivial sighand locking. It's too late in the release cycle for such a change. For now we just keep the timer running and enforce that the timer only fires every jiffie. This does not break anything as we keep the overrun counter correct. It adds a little inaccuracy to the timer_gettime() interface, but... The more complex change is necessary anyway to fix another short coming of the current implementation, which I discovered while looking at this problem: A pending signal is discarded when SIG_IGN is set. In case that a posixtimer signal is pending then it is discarded as well, but when SIG_IGN is removed later nothing rearms the timer. This is not new, it's that way since posix timers have been merged. So nothing to worry about right now. I have a working solution to fix all of this, but the impact is too large for both stable and 2.6.22. I'm going to send it out for review in the next days. This should go into 2.6.21.stable as well. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: Jan Kiszka <jan.kiszka@web.de> Cc: Ulrich Drepper <drepper@redhat.com> Cc: Stable Team <stable@kernel.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-06-21 20:45:15 +00:00
ktime_t now = hrtimer_cb_get_time(timer);
/*
* FIXME: What we really want, is to stop this
* timer completely and restart it in case the
* SIG_IGN is removed. This is a non trivial
* change which involves sighand locking
* (sigh !), which we don't want to do late in
* the release cycle.
*
* For now we just let timers with an interval
* less than a jiffie expire every jiffie to
* avoid softirq starvation in case of SIG_IGN
* and a very small interval, which would put
* the timer right back on the softirq pending
* list. By moving now ahead of time we trick
* hrtimer_forward() to expire the timer
* later, while we still maintain the overrun
* accuracy, but have some inconsistency in
* the timer_gettime() case. This is at least
* better than a starved softirq. A more
* complex fix which solves also another related
* inconsistency is already in the pipeline.
*/
#ifdef CONFIG_HIGH_RES_TIMERS
{
ktime_t kj = ktime_set(0, NSEC_PER_SEC / HZ);
if (timr->it.real.interval.tv64 < kj.tv64)
now = ktime_add(now, kj);
}
#endif
timerfd: new timerfd API This is the new timerfd API as it is implemented by the following patch: int timerfd_create(int clockid, int flags); int timerfd_settime(int ufd, int flags, const struct itimerspec *utmr, struct itimerspec *otmr); int timerfd_gettime(int ufd, struct itimerspec *otmr); The timerfd_create() API creates an un-programmed timerfd fd. The "clockid" parameter can be either CLOCK_MONOTONIC or CLOCK_REALTIME. The timerfd_settime() API give new settings by the timerfd fd, by optionally retrieving the previous expiration time (in case the "otmr" parameter is not NULL). The time value specified in "utmr" is absolute, if the TFD_TIMER_ABSTIME bit is set in the "flags" parameter. Otherwise it's a relative time. The timerfd_gettime() API returns the next expiration time of the timer, or {0, 0} if the timerfd has not been set yet. Like the previous timerfd API implementation, read(2) and poll(2) are supported (with the same interface). Here's a simple test program I used to exercise the new timerfd APIs: http://www.xmailserver.org/timerfd-test2.c [akpm@linux-foundation.org: coding-style cleanups] [akpm@linux-foundation.org: fix ia64 build] [akpm@linux-foundation.org: fix m68k build] [akpm@linux-foundation.org: fix mips build] [akpm@linux-foundation.org: fix alpha, arm, blackfin, cris, m68k, s390, sparc and sparc64 builds] [heiko.carstens@de.ibm.com: fix s390] [akpm@linux-foundation.org: fix powerpc build] [akpm@linux-foundation.org: fix sparc64 more] Signed-off-by: Davide Libenzi <davidel@xmailserver.org> Cc: Michael Kerrisk <mtk-manpages@gmx.net> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Davide Libenzi <davidel@xmailserver.org> Cc: Michael Kerrisk <mtk-manpages@gmx.net> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Davide Libenzi <davidel@xmailserver.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 06:27:26 +00:00
timr->it_overrun += (unsigned int)
posix-timers: Prevent softirq starvation by small intervals and SIG_IGN posix-timers which deliver an ignored signal are currently rearmed in the timer softirq: This is necessary because the timer needs to be delivered again when SIG_IGN is removed. This is not a problem, when the interval is reasonable. With high resolution timers enabled one might arm a posix timer with a very small interval and ignore the signal. This might lead to a softirq starvation when the interval is so small that the timer is requeued onto the softirq pending list right away. This problem was pointed out by Jan Kiszka. Thanks Jan ! The correct solution would be to stop the timer, when the signal is ignored and rearm it when SIG_IGN is removed. Unfortunately this requires modification in sigaction and involves non trivial sighand locking. It's too late in the release cycle for such a change. For now we just keep the timer running and enforce that the timer only fires every jiffie. This does not break anything as we keep the overrun counter correct. It adds a little inaccuracy to the timer_gettime() interface, but... The more complex change is necessary anyway to fix another short coming of the current implementation, which I discovered while looking at this problem: A pending signal is discarded when SIG_IGN is set. In case that a posixtimer signal is pending then it is discarded as well, but when SIG_IGN is removed later nothing rearms the timer. This is not new, it's that way since posix timers have been merged. So nothing to worry about right now. I have a working solution to fix all of this, but the impact is too large for both stable and 2.6.22. I'm going to send it out for review in the next days. This should go into 2.6.21.stable as well. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: Jan Kiszka <jan.kiszka@web.de> Cc: Ulrich Drepper <drepper@redhat.com> Cc: Stable Team <stable@kernel.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-06-21 20:45:15 +00:00
hrtimer_forward(timer, now,
timr->it.real.interval);
ret = HRTIMER_RESTART;
++timr->it_requeue_pending;
}
}
unlock_timer(timr, flags);
return ret;
}
static struct pid *good_sigevent(sigevent_t * event)
{
struct task_struct *rtn = current->group_leader;
if ((event->sigev_notify & SIGEV_THREAD_ID ) &&
(!(rtn = find_task_by_vpid(event->sigev_notify_thread_id)) ||
!same_thread_group(rtn, current) ||
(event->sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_SIGNAL))
return NULL;
if (((event->sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE) &&
((event->sigev_signo <= 0) || (event->sigev_signo > SIGRTMAX)))
return NULL;
return task_pid(rtn);
}
void posix_timers_register_clock(const clockid_t clock_id,
struct k_clock *new_clock)
{
if ((unsigned) clock_id >= MAX_CLOCKS) {
printk(KERN_WARNING "POSIX clock register failed for clock_id %d\n",
clock_id);
return;
}
if (!new_clock->clock_get) {
printk(KERN_WARNING "POSIX clock id %d lacks clock_get()\n",
clock_id);
return;
}
if (!new_clock->clock_getres) {
printk(KERN_WARNING "POSIX clock id %d lacks clock_getres()\n",
clock_id);
return;
}
posix_clocks[clock_id] = *new_clock;
}
EXPORT_SYMBOL_GPL(posix_timers_register_clock);
static struct k_itimer * alloc_posix_timer(void)
{
struct k_itimer *tmr;
tmr = kmem_cache_zalloc(posix_timers_cache, GFP_KERNEL);
if (!tmr)
return tmr;
if (unlikely(!(tmr->sigq = sigqueue_alloc()))) {
kmem_cache_free(posix_timers_cache, tmr);
return NULL;
}
posix-timers: fix posix_timer_event() vs dequeue_signal() race The bug was reported and analysed by Mark McLoughlin <markmc@redhat.com>, the patch is based on his and Roland's suggestions. posix_timer_event() always rewrites the pre-allocated siginfo before sending the signal. Most of the written info is the same all the time, but memset(0) is very wrong. If ->sigq is queued we can race with collect_signal() which can fail to find this siginfo looking at .si_signo, or copy_siginfo() can copy the wrong .si_code/si_tid/etc. In short, sys_timer_settime() can in fact stop the active timer, or the user can receive the siginfo with the wrong .si_xxx values. Move "memset(->info, 0)" from posix_timer_event() to alloc_posix_timer(), change send_sigqueue() to set .si_overrun = 0 when ->sigq is not queued. It would be nice to move the whole sigq->info initialization from send to create path, but this is not easy to do without uglifying timer_create() further. As Roland rightly pointed out, we need more cleanups/fixes here, see the "FIXME" comment in the patch. Hopefully this patch makes sense anyway, and it can mask the most bad implications. Reported-by: Mark McLoughlin <markmc@redhat.com> Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Cc: Mark McLoughlin <markmc@redhat.com> Cc: Oliver Pinter <oliver.pntr@gmail.com> Cc: Roland McGrath <roland@redhat.com> Cc: stable@kernel.org Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> kernel/posix-timers.c | 17 +++++++++++++---- kernel/signal.c | 1 + 2 files changed, 14 insertions(+), 4 deletions(-)
2008-07-23 16:52:05 +00:00
memset(&tmr->sigq->info, 0, sizeof(siginfo_t));
return tmr;
}
static void k_itimer_rcu_free(struct rcu_head *head)
{
struct k_itimer *tmr = container_of(head, struct k_itimer, it.rcu);
kmem_cache_free(posix_timers_cache, tmr);
}
#define IT_ID_SET 1
#define IT_ID_NOT_SET 0
static void release_posix_timer(struct k_itimer *tmr, int it_id_set)
{
if (it_id_set) {
unsigned long flags;
spin_lock_irqsave(&idr_lock, flags);
idr_remove(&posix_timers_id, tmr->it_id);
spin_unlock_irqrestore(&idr_lock, flags);
}
put_pid(tmr->it_pid);
sigqueue_free(tmr->sigq);
call_rcu(&tmr->it.rcu, k_itimer_rcu_free);
}
static struct k_clock *clockid_to_kclock(const clockid_t id)
{
if (id < 0)
return (id & CLOCKFD_MASK) == CLOCKFD ?
&clock_posix_dynamic : &clock_posix_cpu;
if (id >= MAX_CLOCKS || !posix_clocks[id].clock_getres)
return NULL;
return &posix_clocks[id];
}
static int common_timer_create(struct k_itimer *new_timer)
{
hrtimer_init(&new_timer->it.real.timer, new_timer->it_clock, 0);
return 0;
}
/* Create a POSIX.1b interval timer. */
SYSCALL_DEFINE3(timer_create, const clockid_t, which_clock,
struct sigevent __user *, timer_event_spec,
timer_t __user *, created_timer_id)
{
struct k_clock *kc = clockid_to_kclock(which_clock);
struct k_itimer *new_timer;
int error, new_timer_id;
sigevent_t event;
int it_id_set = IT_ID_NOT_SET;
if (!kc)
return -EINVAL;
if (!kc->timer_create)
return -EOPNOTSUPP;
new_timer = alloc_posix_timer();
if (unlikely(!new_timer))
return -EAGAIN;
spin_lock_init(&new_timer->it_lock);
retry:
if (unlikely(!idr_pre_get(&posix_timers_id, GFP_KERNEL))) {
error = -EAGAIN;
goto out;
}
spin_lock_irq(&idr_lock);
error = idr_get_new(&posix_timers_id, new_timer, &new_timer_id);
spin_unlock_irq(&idr_lock);
if (error) {
if (error == -EAGAIN)
goto retry;
/*
* Weird looking, but we return EAGAIN if the IDR is
* full (proper POSIX return value for this)
*/
error = -EAGAIN;
goto out;
}
it_id_set = IT_ID_SET;
new_timer->it_id = (timer_t) new_timer_id;
new_timer->it_clock = which_clock;
new_timer->it_overrun = -1;
if (timer_event_spec) {
if (copy_from_user(&event, timer_event_spec, sizeof (event))) {
error = -EFAULT;
goto out;
}
rcu_read_lock();
new_timer->it_pid = get_pid(good_sigevent(&event));
rcu_read_unlock();
if (!new_timer->it_pid) {
error = -EINVAL;
goto out;
}
} else {
event.sigev_notify = SIGEV_SIGNAL;
event.sigev_signo = SIGALRM;
event.sigev_value.sival_int = new_timer->it_id;
new_timer->it_pid = get_pid(task_tgid(current));
}
new_timer->it_sigev_notify = event.sigev_notify;
new_timer->sigq->info.si_signo = event.sigev_signo;
new_timer->sigq->info.si_value = event.sigev_value;
new_timer->sigq->info.si_tid = new_timer->it_id;
new_timer->sigq->info.si_code = SI_TIMER;
if (copy_to_user(created_timer_id,
&new_timer_id, sizeof (new_timer_id))) {
error = -EFAULT;
goto out;
}
error = kc->timer_create(new_timer);
if (error)
goto out;
spin_lock_irq(&current->sighand->siglock);
new_timer->it_signal = current->signal;
list_add(&new_timer->list, &current->signal->posix_timers);
spin_unlock_irq(&current->sighand->siglock);
return 0;
/*
* In the case of the timer belonging to another task, after
* the task is unlocked, the timer is owned by the other task
* and may cease to exist at any time. Don't use or modify
* new_timer after the unlock call.
*/
out:
release_posix_timer(new_timer, it_id_set);
return error;
}
/*
* Locking issues: We need to protect the result of the id look up until
* we get the timer locked down so it is not deleted under us. The
* removal is done under the idr spinlock so we use that here to bridge
* the find to the timer lock. To avoid a dead lock, the timer id MUST
* be release with out holding the timer lock.
*/
static struct k_itimer *__lock_timer(timer_t timer_id, unsigned long *flags)
{
struct k_itimer *timr;
rcu_read_lock();
timr = idr_find(&posix_timers_id, (int)timer_id);
if (timr) {
spin_lock_irqsave(&timr->it_lock, *flags);
if (timr->it_signal == current->signal) {
rcu_read_unlock();
return timr;
}
spin_unlock_irqrestore(&timr->it_lock, *flags);
}
rcu_read_unlock();
return NULL;
}
/*
* Get the time remaining on a POSIX.1b interval timer. This function
* is ALWAYS called with spin_lock_irq on the timer, thus it must not
* mess with irq.
*
* We have a couple of messes to clean up here. First there is the case
* of a timer that has a requeue pending. These timers should appear to
* be in the timer list with an expiry as if we were to requeue them
* now.
*
* The second issue is the SIGEV_NONE timer which may be active but is
* not really ever put in the timer list (to save system resources).
* This timer may be expired, and if so, we will do it here. Otherwise
* it is the same as a requeue pending timer WRT to what we should
* report.
*/
static void
common_timer_get(struct k_itimer *timr, struct itimerspec *cur_setting)
{
ktime_t now, remaining, iv;
struct hrtimer *timer = &timr->it.real.timer;
memset(cur_setting, 0, sizeof(struct itimerspec));
iv = timr->it.real.interval;
/* interval timer ? */
if (iv.tv64)
cur_setting->it_interval = ktime_to_timespec(iv);
else if (!hrtimer_active(timer) &&
(timr->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE)
return;
now = timer->base->get_time();
/*
* When a requeue is pending or this is a SIGEV_NONE
* timer move the expiry time forward by intervals, so
* expiry is > now.
*/
if (iv.tv64 && (timr->it_requeue_pending & REQUEUE_PENDING ||
(timr->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE))
timerfd: new timerfd API This is the new timerfd API as it is implemented by the following patch: int timerfd_create(int clockid, int flags); int timerfd_settime(int ufd, int flags, const struct itimerspec *utmr, struct itimerspec *otmr); int timerfd_gettime(int ufd, struct itimerspec *otmr); The timerfd_create() API creates an un-programmed timerfd fd. The "clockid" parameter can be either CLOCK_MONOTONIC or CLOCK_REALTIME. The timerfd_settime() API give new settings by the timerfd fd, by optionally retrieving the previous expiration time (in case the "otmr" parameter is not NULL). The time value specified in "utmr" is absolute, if the TFD_TIMER_ABSTIME bit is set in the "flags" parameter. Otherwise it's a relative time. The timerfd_gettime() API returns the next expiration time of the timer, or {0, 0} if the timerfd has not been set yet. Like the previous timerfd API implementation, read(2) and poll(2) are supported (with the same interface). Here's a simple test program I used to exercise the new timerfd APIs: http://www.xmailserver.org/timerfd-test2.c [akpm@linux-foundation.org: coding-style cleanups] [akpm@linux-foundation.org: fix ia64 build] [akpm@linux-foundation.org: fix m68k build] [akpm@linux-foundation.org: fix mips build] [akpm@linux-foundation.org: fix alpha, arm, blackfin, cris, m68k, s390, sparc and sparc64 builds] [heiko.carstens@de.ibm.com: fix s390] [akpm@linux-foundation.org: fix powerpc build] [akpm@linux-foundation.org: fix sparc64 more] Signed-off-by: Davide Libenzi <davidel@xmailserver.org> Cc: Michael Kerrisk <mtk-manpages@gmx.net> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Davide Libenzi <davidel@xmailserver.org> Cc: Michael Kerrisk <mtk-manpages@gmx.net> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Davide Libenzi <davidel@xmailserver.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 06:27:26 +00:00
timr->it_overrun += (unsigned int) hrtimer_forward(timer, now, iv);
remaining = ktime_sub(hrtimer_get_expires(timer), now);
/* Return 0 only, when the timer is expired and not pending */
if (remaining.tv64 <= 0) {
/*
* A single shot SIGEV_NONE timer must return 0, when
* it is expired !
*/
if ((timr->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE)
cur_setting->it_value.tv_nsec = 1;
} else
cur_setting->it_value = ktime_to_timespec(remaining);
}
/* Get the time remaining on a POSIX.1b interval timer. */
SYSCALL_DEFINE2(timer_gettime, timer_t, timer_id,
struct itimerspec __user *, setting)
{
struct itimerspec cur_setting;
struct k_itimer *timr;
struct k_clock *kc;
unsigned long flags;
int ret = 0;
timr = lock_timer(timer_id, &flags);
if (!timr)
return -EINVAL;
kc = clockid_to_kclock(timr->it_clock);
if (WARN_ON_ONCE(!kc || !kc->timer_get))
ret = -EINVAL;
else
kc->timer_get(timr, &cur_setting);
unlock_timer(timr, flags);
if (!ret && copy_to_user(setting, &cur_setting, sizeof (cur_setting)))
return -EFAULT;
return ret;
}
/*
* Get the number of overruns of a POSIX.1b interval timer. This is to
* be the overrun of the timer last delivered. At the same time we are
* accumulating overruns on the next timer. The overrun is frozen when
* the signal is delivered, either at the notify time (if the info block
* is not queued) or at the actual delivery time (as we are informed by
* the call back to do_schedule_next_timer(). So all we need to do is
* to pick up the frozen overrun.
*/
SYSCALL_DEFINE1(timer_getoverrun, timer_t, timer_id)
{
struct k_itimer *timr;
int overrun;
unsigned long flags;
timr = lock_timer(timer_id, &flags);
if (!timr)
return -EINVAL;
overrun = timr->it_overrun_last;
unlock_timer(timr, flags);
return overrun;
}
/* Set a POSIX.1b interval timer. */
/* timr->it_lock is taken. */
static int
common_timer_set(struct k_itimer *timr, int flags,
struct itimerspec *new_setting, struct itimerspec *old_setting)
{
struct hrtimer *timer = &timr->it.real.timer;
enum hrtimer_mode mode;
if (old_setting)
common_timer_get(timr, old_setting);
/* disable the timer */
timr->it.real.interval.tv64 = 0;
/*
* careful here. If smp we could be in the "fire" routine which will
* be spinning as we hold the lock. But this is ONLY an SMP issue.
*/
if (hrtimer_try_to_cancel(timer) < 0)
return TIMER_RETRY;
timr->it_requeue_pending = (timr->it_requeue_pending + 2) &
~REQUEUE_PENDING;
timr->it_overrun_last = 0;
/* switch off the timer when it_value is zero */
if (!new_setting->it_value.tv_sec && !new_setting->it_value.tv_nsec)
return 0;
mode = flags & TIMER_ABSTIME ? HRTIMER_MODE_ABS : HRTIMER_MODE_REL;
hrtimer_init(&timr->it.real.timer, timr->it_clock, mode);
timr->it.real.timer.function = posix_timer_fn;
hrtimer_set_expires(timer, timespec_to_ktime(new_setting->it_value));
/* Convert interval */
timr->it.real.interval = timespec_to_ktime(new_setting->it_interval);
/* SIGEV_NONE timers are not queued ! See common_timer_get */
if (((timr->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE)) {
/* Setup correct expiry time for relative timers */
if (mode == HRTIMER_MODE_REL) {
hrtimer_add_expires(timer, timer->base->get_time());
}
return 0;
}
hrtimer_start_expires(timer, mode);
return 0;
}
/* Set a POSIX.1b interval timer */
SYSCALL_DEFINE4(timer_settime, timer_t, timer_id, int, flags,
const struct itimerspec __user *, new_setting,
struct itimerspec __user *, old_setting)
{
struct k_itimer *timr;
struct itimerspec new_spec, old_spec;
int error = 0;
unsigned long flag;
struct itimerspec *rtn = old_setting ? &old_spec : NULL;
struct k_clock *kc;
if (!new_setting)
return -EINVAL;
if (copy_from_user(&new_spec, new_setting, sizeof (new_spec)))
return -EFAULT;
if (!timespec_valid(&new_spec.it_interval) ||
!timespec_valid(&new_spec.it_value))
return -EINVAL;
retry:
timr = lock_timer(timer_id, &flag);
if (!timr)
return -EINVAL;
kc = clockid_to_kclock(timr->it_clock);
if (WARN_ON_ONCE(!kc || !kc->timer_set))
error = -EINVAL;
else
error = kc->timer_set(timr, flags, &new_spec, rtn);
unlock_timer(timr, flag);
if (error == TIMER_RETRY) {
rtn = NULL; // We already got the old time...
goto retry;
}
if (old_setting && !error &&
copy_to_user(old_setting, &old_spec, sizeof (old_spec)))
error = -EFAULT;
return error;
}
static int common_timer_del(struct k_itimer *timer)
{
timer->it.real.interval.tv64 = 0;
if (hrtimer_try_to_cancel(&timer->it.real.timer) < 0)
return TIMER_RETRY;
return 0;
}
static inline int timer_delete_hook(struct k_itimer *timer)
{
struct k_clock *kc = clockid_to_kclock(timer->it_clock);
if (WARN_ON_ONCE(!kc || !kc->timer_del))
return -EINVAL;
return kc->timer_del(timer);
}
/* Delete a POSIX.1b interval timer. */
SYSCALL_DEFINE1(timer_delete, timer_t, timer_id)
{
struct k_itimer *timer;
unsigned long flags;
retry_delete:
timer = lock_timer(timer_id, &flags);
if (!timer)
return -EINVAL;
if (timer_delete_hook(timer) == TIMER_RETRY) {
unlock_timer(timer, flags);
goto retry_delete;
}
spin_lock(&current->sighand->siglock);
list_del(&timer->list);
spin_unlock(&current->sighand->siglock);
/*
* This keeps any tasks waiting on the spin lock from thinking
* they got something (see the lock code above).
*/
timer->it_signal = NULL;
unlock_timer(timer, flags);
release_posix_timer(timer, IT_ID_SET);
return 0;
}
/*
* return timer owned by the process, used by exit_itimers
*/
static void itimer_delete(struct k_itimer *timer)
{
unsigned long flags;
retry_delete:
spin_lock_irqsave(&timer->it_lock, flags);
if (timer_delete_hook(timer) == TIMER_RETRY) {
unlock_timer(timer, flags);
goto retry_delete;
}
list_del(&timer->list);
/*
* This keeps any tasks waiting on the spin lock from thinking
* they got something (see the lock code above).
*/
timer->it_signal = NULL;
unlock_timer(timer, flags);
release_posix_timer(timer, IT_ID_SET);
}
/*
* This is called by do_exit or de_thread, only when there are no more
* references to the shared signal_struct.
*/
void exit_itimers(struct signal_struct *sig)
{
struct k_itimer *tmr;
while (!list_empty(&sig->posix_timers)) {
tmr = list_entry(sig->posix_timers.next, struct k_itimer, list);
itimer_delete(tmr);
}
}
SYSCALL_DEFINE2(clock_settime, const clockid_t, which_clock,
const struct timespec __user *, tp)
{
struct k_clock *kc = clockid_to_kclock(which_clock);
struct timespec new_tp;
if (!kc || !kc->clock_set)
return -EINVAL;
if (copy_from_user(&new_tp, tp, sizeof (*tp)))
return -EFAULT;
return kc->clock_set(which_clock, &new_tp);
}
SYSCALL_DEFINE2(clock_gettime, const clockid_t, which_clock,
struct timespec __user *,tp)
{
struct k_clock *kc = clockid_to_kclock(which_clock);
struct timespec kernel_tp;
int error;
if (!kc)
return -EINVAL;
error = kc->clock_get(which_clock, &kernel_tp);
if (!error && copy_to_user(tp, &kernel_tp, sizeof (kernel_tp)))
error = -EFAULT;
return error;
}
SYSCALL_DEFINE2(clock_adjtime, const clockid_t, which_clock,
struct timex __user *, utx)
{
struct k_clock *kc = clockid_to_kclock(which_clock);
struct timex ktx;
int err;
if (!kc)
return -EINVAL;
if (!kc->clock_adj)
return -EOPNOTSUPP;
if (copy_from_user(&ktx, utx, sizeof(ktx)))
return -EFAULT;
err = kc->clock_adj(which_clock, &ktx);
if (!err && copy_to_user(utx, &ktx, sizeof(ktx)))
return -EFAULT;
return err;
}
SYSCALL_DEFINE2(clock_getres, const clockid_t, which_clock,
struct timespec __user *, tp)
{
struct k_clock *kc = clockid_to_kclock(which_clock);
struct timespec rtn_tp;
int error;
if (!kc)
return -EINVAL;
error = kc->clock_getres(which_clock, &rtn_tp);
if (!error && tp && copy_to_user(tp, &rtn_tp, sizeof (rtn_tp)))
error = -EFAULT;
return error;
}
/*
* nanosleep for monotonic and realtime clocks
*/
static int common_nsleep(const clockid_t which_clock, int flags,
struct timespec *tsave, struct timespec __user *rmtp)
{
hrtimer: fix *rmtp handling in hrtimer_nanosleep() Spotted by Pavel Emelyanov and Alexey Dobriyan. hrtimer_nanosleep() sets restart_block->arg1 = rmtp, but this rmtp points to the local variable which lives in the caller's stack frame. This means that if sys_restart_syscall() actually happens and it is interrupted as well, we don't update the user-space variable, but write into the already dead stack frame. Introduced by commit 04c227140fed77587432667a574b14736a06dd7f hrtimer: Rework hrtimer_nanosleep to make sys_compat_nanosleep easier Change the callers to pass "__user *rmtp" to hrtimer_nanosleep(), and change hrtimer_nanosleep() to use copy_to_user() to actually update *rmtp. Small problem remains. man 2 nanosleep states that *rtmp should be written if nanosleep() was interrupted (it says nothing whether it is OK to update *rmtp if nanosleep returns 0), but (with or without this patch) we can dirty *rem even if nanosleep() returns 0. NOTE: this patch doesn't change compat_sys_nanosleep(), because it has other bugs. Fixed by the next patch. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Cc: Alexey Dobriyan <adobriyan@sw.ru> Cc: Michael Kerrisk <mtk.manpages@googlemail.com> Cc: Pavel Emelyanov <xemul@sw.ru> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Toyo Abe <toyoa@mvista.com> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> include/linux/hrtimer.h | 2 - kernel/hrtimer.c | 51 +++++++++++++++++++++++++----------------------- kernel/posix-timers.c | 14 +------------ 3 files changed, 30 insertions(+), 37 deletions(-)
2008-02-01 14:29:05 +00:00
return hrtimer_nanosleep(tsave, rmtp, flags & TIMER_ABSTIME ?
HRTIMER_MODE_ABS : HRTIMER_MODE_REL,
which_clock);
}
SYSCALL_DEFINE4(clock_nanosleep, const clockid_t, which_clock, int, flags,
const struct timespec __user *, rqtp,
struct timespec __user *, rmtp)
{
struct k_clock *kc = clockid_to_kclock(which_clock);
struct timespec t;
if (!kc)
return -EINVAL;
if (!kc->nsleep)
return -ENANOSLEEP_NOTSUP;
if (copy_from_user(&t, rqtp, sizeof (struct timespec)))
return -EFAULT;
if (!timespec_valid(&t))
return -EINVAL;
return kc->nsleep(which_clock, flags, &t, rmtp);
}
/*
* This will restart clock_nanosleep. This is required only by
* compat_clock_nanosleep_restart for now.
*/
long clock_nanosleep_restart(struct restart_block *restart_block)
{
clockid_t which_clock = restart_block->nanosleep.clockid;
struct k_clock *kc = clockid_to_kclock(which_clock);
if (WARN_ON_ONCE(!kc || !kc->nsleep_restart))
return -EINVAL;
return kc->nsleep_restart(restart_block);
}