![John Stultz](/assets/img/avatar_default.png)
This patch exposes alarm-timers to userland via the posix clock and timers interface, using two new clockids: CLOCK_REALTIME_ALARM and CLOCK_BOOTTIME_ALARM. Both clockids behave identically to CLOCK_REALTIME and CLOCK_BOOTTIME, respectively, but timers set against the _ALARM suffixed clockids will wake the system if it is suspended. Some background can be found here: https://lwn.net/Articles/429925/ The concept for Alarm-timers was inspired by the Android Alarm driver (by Arve Hjønnevåg) found in the Android kernel tree. See: http://android.git.kernel.org/?p=kernel/common.git;a=blob;f=drivers/rtc/alarm.c;h=1250edfbdf3302f5e4ea6194847c6ef4bb7beb1c;hb=android-2.6.36 While the in-kernel interface is pretty similar between alarm-timers and Android alarm driver, the user-space interface for the Android alarm driver is via ioctls to a new char device. As mentioned above, I've instead chosen to export this functionality via the posix interface, as it seemed a little simpler and avoids creating duplicate interfaces to things like CLOCK_REALTIME and CLOCK_MONOTONIC under alternate names (ie:ANDROID_ALARM_RTC and ANDROID_ALARM_SYSTEMTIME). The semantics of the Android alarm driver are different from what this posix interface provides. For instance, threads other then the thread waiting on the Android alarm driver are able to modify the alarm being waited on. Also this interface does not allow the same wakelock semantics that the Android driver provides (ie: kernel takes a wakelock on RTC alarm-interupt, and holds it through process wakeup, and while the process runs, until the process either closes the char device or calls back in to wait on a new alarm). One potential way to implement similar semantics may be via the timerfd infrastructure, but this needs more research. There may also need to be some sort of sysfs system level policy hooks that allow alarm timers to be disabled to keep them from firing at inappropriate times (ie: laptop in a well insulated bag, mid-flight). CC: Arve Hjønnevåg <arve@android.com> CC: Thomas Gleixner <tglx@linutronix.de> CC: Alessandro Zummo <a.zummo@towertech.it> Acked-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: John Stultz <john.stultz@linaro.org>
129 lines
4 KiB
C
129 lines
4 KiB
C
#ifndef _linux_POSIX_TIMERS_H
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#define _linux_POSIX_TIMERS_H
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#include <linux/spinlock.h>
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#include <linux/list.h>
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#include <linux/sched.h>
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#include <linux/timex.h>
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#include <linux/alarmtimer.h>
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union cpu_time_count {
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cputime_t cpu;
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unsigned long long sched;
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};
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struct cpu_timer_list {
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struct list_head entry;
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union cpu_time_count expires, incr;
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struct task_struct *task;
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int firing;
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};
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/*
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* Bit fields within a clockid:
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*
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* The most significant 29 bits hold either a pid or a file descriptor.
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*
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* Bit 2 indicates whether a cpu clock refers to a thread or a process.
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*
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* Bits 1 and 0 give the type: PROF=0, VIRT=1, SCHED=2, or FD=3.
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*
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* A clockid is invalid if bits 2, 1, and 0 are all set.
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*/
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#define CPUCLOCK_PID(clock) ((pid_t) ~((clock) >> 3))
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#define CPUCLOCK_PERTHREAD(clock) \
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(((clock) & (clockid_t) CPUCLOCK_PERTHREAD_MASK) != 0)
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#define CPUCLOCK_PERTHREAD_MASK 4
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#define CPUCLOCK_WHICH(clock) ((clock) & (clockid_t) CPUCLOCK_CLOCK_MASK)
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#define CPUCLOCK_CLOCK_MASK 3
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#define CPUCLOCK_PROF 0
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#define CPUCLOCK_VIRT 1
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#define CPUCLOCK_SCHED 2
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#define CPUCLOCK_MAX 3
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#define CLOCKFD CPUCLOCK_MAX
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#define CLOCKFD_MASK (CPUCLOCK_PERTHREAD_MASK|CPUCLOCK_CLOCK_MASK)
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#define MAKE_PROCESS_CPUCLOCK(pid, clock) \
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((~(clockid_t) (pid) << 3) | (clockid_t) (clock))
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#define MAKE_THREAD_CPUCLOCK(tid, clock) \
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MAKE_PROCESS_CPUCLOCK((tid), (clock) | CPUCLOCK_PERTHREAD_MASK)
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#define FD_TO_CLOCKID(fd) ((~(clockid_t) (fd) << 3) | CLOCKFD)
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#define CLOCKID_TO_FD(clk) ((unsigned int) ~((clk) >> 3))
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/* POSIX.1b interval timer structure. */
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struct k_itimer {
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struct list_head list; /* free/ allocate list */
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spinlock_t it_lock;
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clockid_t it_clock; /* which timer type */
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timer_t it_id; /* timer id */
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int it_overrun; /* overrun on pending signal */
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int it_overrun_last; /* overrun on last delivered signal */
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int it_requeue_pending; /* waiting to requeue this timer */
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#define REQUEUE_PENDING 1
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int it_sigev_notify; /* notify word of sigevent struct */
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struct signal_struct *it_signal;
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union {
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struct pid *it_pid; /* pid of process to send signal to */
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struct task_struct *it_process; /* for clock_nanosleep */
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};
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struct sigqueue *sigq; /* signal queue entry. */
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union {
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struct {
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struct hrtimer timer;
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ktime_t interval;
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} real;
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struct cpu_timer_list cpu;
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struct {
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unsigned int clock;
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unsigned int node;
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unsigned long incr;
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unsigned long expires;
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} mmtimer;
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struct alarm alarmtimer;
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} it;
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};
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struct k_clock {
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int (*clock_getres) (const clockid_t which_clock, struct timespec *tp);
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int (*clock_set) (const clockid_t which_clock,
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const struct timespec *tp);
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int (*clock_get) (const clockid_t which_clock, struct timespec * tp);
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int (*clock_adj) (const clockid_t which_clock, struct timex *tx);
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int (*timer_create) (struct k_itimer *timer);
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int (*nsleep) (const clockid_t which_clock, int flags,
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struct timespec *, struct timespec __user *);
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long (*nsleep_restart) (struct restart_block *restart_block);
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int (*timer_set) (struct k_itimer * timr, int flags,
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struct itimerspec * new_setting,
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struct itimerspec * old_setting);
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int (*timer_del) (struct k_itimer * timr);
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#define TIMER_RETRY 1
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void (*timer_get) (struct k_itimer * timr,
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struct itimerspec * cur_setting);
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};
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extern struct k_clock clock_posix_cpu;
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extern struct k_clock clock_posix_dynamic;
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void posix_timers_register_clock(const clockid_t clock_id, struct k_clock *new_clock);
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/* function to call to trigger timer event */
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int posix_timer_event(struct k_itimer *timr, int si_private);
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void posix_cpu_timer_schedule(struct k_itimer *timer);
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void run_posix_cpu_timers(struct task_struct *task);
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void posix_cpu_timers_exit(struct task_struct *task);
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void posix_cpu_timers_exit_group(struct task_struct *task);
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void set_process_cpu_timer(struct task_struct *task, unsigned int clock_idx,
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cputime_t *newval, cputime_t *oldval);
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long clock_nanosleep_restart(struct restart_block *restart_block);
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void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new);
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#endif
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