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timerfd: Add alarm timers

Add support for clocks CLOCK_REALTIME_ALARM and CLOCK_BOOTTIME_ALARM,
thereby enabling wakeup alarm timers via file descriptors.

Signed-off-by: Todd Poynor <toddpoynor@google.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
master
Todd Poynor 8 years ago
committed by John Stultz
parent
commit
11ffa9d606
  1. 131
      fs/timerfd.c

131
fs/timerfd.c

@ -8,6 +8,7 @@
*
*/
#include <linux/alarmtimer.h>
#include <linux/file.h>
#include <linux/poll.h>
#include <linux/init.h>
@ -26,7 +27,10 @@
#include <linux/rcupdate.h>
struct timerfd_ctx {
struct hrtimer tmr;
union {
struct hrtimer tmr;
struct alarm alarm;
} t;
ktime_t tintv;
ktime_t moffs;
wait_queue_head_t wqh;
@ -41,14 +45,19 @@ struct timerfd_ctx {
static LIST_HEAD(cancel_list);
static DEFINE_SPINLOCK(cancel_lock);
static inline bool isalarm(struct timerfd_ctx *ctx)
{
return ctx->clockid == CLOCK_REALTIME_ALARM ||
ctx->clockid == CLOCK_BOOTTIME_ALARM;
}
/*
* This gets called when the timer event triggers. We set the "expired"
* flag, but we do not re-arm the timer (in case it's necessary,
* tintv.tv64 != 0) until the timer is accessed.
*/
static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr)
static void timerfd_triggered(struct timerfd_ctx *ctx)
{
struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx, tmr);
unsigned long flags;
spin_lock_irqsave(&ctx->wqh.lock, flags);
@ -56,10 +65,25 @@ static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr)
ctx->ticks++;
wake_up_locked(&ctx->wqh);
spin_unlock_irqrestore(&ctx->wqh.lock, flags);
}
static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr)
{
struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx,
t.tmr);
timerfd_triggered(ctx);
return HRTIMER_NORESTART;
}
static enum alarmtimer_restart timerfd_alarmproc(struct alarm *alarm,
ktime_t now)
{
struct timerfd_ctx *ctx = container_of(alarm, struct timerfd_ctx,
t.alarm);
timerfd_triggered(ctx);
return ALARMTIMER_NORESTART;
}
/*
* Called when the clock was set to cancel the timers in the cancel
* list. This will wake up processes waiting on these timers. The
@ -107,8 +131,9 @@ static bool timerfd_canceled(struct timerfd_ctx *ctx)
static void timerfd_setup_cancel(struct timerfd_ctx *ctx, int flags)
{
if (ctx->clockid == CLOCK_REALTIME && (flags & TFD_TIMER_ABSTIME) &&
(flags & TFD_TIMER_CANCEL_ON_SET)) {
if ((ctx->clockid == CLOCK_REALTIME ||
ctx->clockid == CLOCK_REALTIME_ALARM) &&
(flags & TFD_TIMER_ABSTIME) && (flags & TFD_TIMER_CANCEL_ON_SET)) {
if (!ctx->might_cancel) {
ctx->might_cancel = true;
spin_lock(&cancel_lock);
@ -124,7 +149,11 @@ static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx)
{
ktime_t remaining;
remaining = hrtimer_expires_remaining(&ctx->tmr);
if (isalarm(ctx))
remaining = alarm_expires_remaining(&ctx->t.alarm);
else
remaining = hrtimer_expires_remaining(&ctx->t.tmr);
return remaining.tv64 < 0 ? ktime_set(0, 0): remaining;
}
@ -142,11 +171,28 @@ static int timerfd_setup(struct timerfd_ctx *ctx, int flags,
ctx->expired = 0;
ctx->ticks = 0;
ctx->tintv = timespec_to_ktime(ktmr->it_interval);
hrtimer_init(&ctx->tmr, clockid, htmode);
hrtimer_set_expires(&ctx->tmr, texp);
ctx->tmr.function = timerfd_tmrproc;
if (isalarm(ctx)) {
alarm_init(&ctx->t.alarm,
ctx->clockid == CLOCK_REALTIME_ALARM ?
ALARM_REALTIME : ALARM_BOOTTIME,
timerfd_alarmproc);
} else {
hrtimer_init(&ctx->t.tmr, clockid, htmode);
hrtimer_set_expires(&ctx->t.tmr, texp);
ctx->t.tmr.function = timerfd_tmrproc;
}
if (texp.tv64 != 0) {
hrtimer_start(&ctx->tmr, texp, htmode);
if (isalarm(ctx)) {
if (flags & TFD_TIMER_ABSTIME)
alarm_start(&ctx->t.alarm, texp);
else
alarm_start_relative(&ctx->t.alarm, texp);
} else {
hrtimer_start(&ctx->t.tmr, texp, htmode);
}
if (timerfd_canceled(ctx))
return -ECANCELED;
}
@ -158,7 +204,11 @@ static int timerfd_release(struct inode *inode, struct file *file)
struct timerfd_ctx *ctx = file->private_data;
timerfd_remove_cancel(ctx);
hrtimer_cancel(&ctx->tmr);
if (isalarm(ctx))
alarm_cancel(&ctx->t.alarm);
else
hrtimer_cancel(&ctx->t.tmr);
kfree_rcu(ctx, rcu);
return 0;
}
@ -215,9 +265,15 @@ static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count,
* callback to avoid DoS attacks specifying a very
* short timer period.
*/
ticks += hrtimer_forward_now(&ctx->tmr,
ctx->tintv) - 1;
hrtimer_restart(&ctx->tmr);
if (isalarm(ctx)) {
ticks += alarm_forward_now(
&ctx->t.alarm, ctx->tintv) - 1;
alarm_restart(&ctx->t.alarm);
} else {
ticks += hrtimer_forward_now(&ctx->t.tmr,
ctx->tintv) - 1;
hrtimer_restart(&ctx->t.tmr);
}
}
ctx->expired = 0;
ctx->ticks = 0;
@ -259,7 +315,9 @@ SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
if ((flags & ~TFD_CREATE_FLAGS) ||
(clockid != CLOCK_MONOTONIC &&
clockid != CLOCK_REALTIME))
clockid != CLOCK_REALTIME &&
clockid != CLOCK_REALTIME_ALARM &&
clockid != CLOCK_BOOTTIME_ALARM))
return -EINVAL;
ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
@ -268,7 +326,15 @@ SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
init_waitqueue_head(&ctx->wqh);
ctx->clockid = clockid;
hrtimer_init(&ctx->tmr, clockid, HRTIMER_MODE_ABS);
if (isalarm(ctx))
alarm_init(&ctx->t.alarm,
ctx->clockid == CLOCK_REALTIME_ALARM ?
ALARM_REALTIME : ALARM_BOOTTIME,
timerfd_alarmproc);
else
hrtimer_init(&ctx->t.tmr, clockid, HRTIMER_MODE_ABS);
ctx->moffs = ktime_get_monotonic_offset();
ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx,
@ -305,8 +371,14 @@ static int do_timerfd_settime(int ufd, int flags,
*/
for (;;) {
spin_lock_irq(&ctx->wqh.lock);
if (hrtimer_try_to_cancel(&ctx->tmr) >= 0)
break;
if (isalarm(ctx)) {
if (alarm_try_to_cancel(&ctx->t.alarm) >= 0)
break;
} else {
if (hrtimer_try_to_cancel(&ctx->t.tmr) >= 0)
break;
}
spin_unlock_irq(&ctx->wqh.lock);
cpu_relax();
}
@ -317,8 +389,12 @@ static int do_timerfd_settime(int ufd, int flags,
* We do not update "ticks" and "expired" since the timer will be
* re-programmed again in the following timerfd_setup() call.
*/
if (ctx->expired && ctx->tintv.tv64)
hrtimer_forward_now(&ctx->tmr, ctx->tintv);
if (ctx->expired && ctx->tintv.tv64) {
if (isalarm(ctx))
alarm_forward_now(&ctx->t.alarm, ctx->tintv);
else
hrtimer_forward_now(&ctx->t.tmr, ctx->tintv);
}
old->it_value = ktime_to_timespec(timerfd_get_remaining(ctx));
old->it_interval = ktime_to_timespec(ctx->tintv);
@ -345,9 +421,18 @@ static int do_timerfd_gettime(int ufd, struct itimerspec *t)
spin_lock_irq(&ctx->wqh.lock);
if (ctx->expired && ctx->tintv.tv64) {
ctx->expired = 0;
ctx->ticks +=
hrtimer_forward_now(&ctx->tmr, ctx->tintv) - 1;
hrtimer_restart(&ctx->tmr);
if (isalarm(ctx)) {
ctx->ticks +=
alarm_forward_now(
&ctx->t.alarm, ctx->tintv) - 1;
alarm_restart(&ctx->t.alarm);
} else {
ctx->ticks +=
hrtimer_forward_now(&ctx->t.tmr, ctx->tintv)
- 1;
hrtimer_restart(&ctx->t.tmr);
}
}
t->it_value = ktime_to_timespec(timerfd_get_remaining(ctx));
t->it_interval = ktime_to_timespec(ctx->tintv);

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