6 files changed, 111 insertions, 8 deletions

diff --git a/fs/timerfd.c b/fs/timerfd.c
index 8c4fc1425b3e..7e14c9e7c4ee 100644
--- a/fs/timerfd.c
+++ b/fs/timerfd.c
@@ -26,10 +26,12 @@
 struct timerfd_ctx {
         struct hrtimer tmr;
         ktime_t tintv;
+        ktime_t moffs;
         wait_queue_head_t wqh;
         u64 ticks;
         int expired;
         int clockid;
+        bool might_cancel;
 };
 
 /*
@@ -59,24 +61,52 @@ static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx)
         return remaining.tv64 < 0 ? ktime_set(0, 0): remaining;
 }
 
-static void timerfd_setup(struct timerfd_ctx *ctx, int flags,
-                          const struct itimerspec *ktmr)
+static bool timerfd_canceled(struct timerfd_ctx *ctx)
+{
+        ktime_t moffs;
+
+        if (!ctx->might_cancel)
+                return false;
+
+        moffs = ktime_get_monotonic_offset();
+
+        if (moffs.tv64 == ctx->moffs.tv64)
+                return false;
+
+        ctx->moffs = moffs;
+        return true;
+}
+
+static int timerfd_setup(struct timerfd_ctx *ctx, int flags,
+                         const struct itimerspec *ktmr)
 {
         enum hrtimer_mode htmode;
         ktime_t texp;
+        int clockid = ctx->clockid;
 
         htmode = (flags & TFD_TIMER_ABSTIME) ?
                 HRTIMER_MODE_ABS: HRTIMER_MODE_REL;
 
+        ctx->might_cancel = false;
+        if (htmode == HRTIMER_MODE_ABS && ctx->clockid == CLOCK_REALTIME &&
+            (flags & TFD_TIMER_CANCELON_SET)) {
+                clockid = CLOCK_REALTIME_COS;
+                ctx->might_cancel = true;
+        }
+
         texp = timespec_to_ktime(ktmr->it_value);
         ctx->expired = 0;
         ctx->ticks = 0;
         ctx->tintv = timespec_to_ktime(ktmr->it_interval);
-        hrtimer_init(&ctx->tmr, ctx->clockid, htmode);
+        hrtimer_init(&ctx->tmr, clockid, htmode);
         hrtimer_set_expires(&ctx->tmr, texp);
         ctx->tmr.function = timerfd_tmrproc;
-        if (texp.tv64 != 0)
+        if (texp.tv64 != 0) {
                 hrtimer_start(&ctx->tmr, texp, htmode);
+                if (timerfd_canceled(ctx))
+                        return -ECANCELED;
+        }
+        return 0;
 }
 
 static int timerfd_release(struct inode *inode, struct file *file)
@@ -118,8 +148,21 @@ static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count,
                 res = -EAGAIN;
         else
                 res = wait_event_interruptible_locked_irq(ctx->wqh, ctx->ticks);
+
         if (ctx->ticks) {
                 ticks = ctx->ticks;
+
+                /*
+                 * If clock has changed, we do not care about the
+                 * ticks and we do not rearm the timer. Userspace must
+                 * reevaluate anyway.
+                 */
+                if (timerfd_canceled(ctx)) {
+                        ticks = 0;
+                        ctx->expired = 0;
+                        res = -ECANCELED;
+                }
+
                 if (ctx->expired && ctx->tintv.tv64) {
                         /*
                          * If tintv.tv64 != 0, this is a periodic timer that
@@ -183,6 +226,7 @@ SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
         init_waitqueue_head(&ctx->wqh);
         ctx->clockid = clockid;
         hrtimer_init(&ctx->tmr, clockid, HRTIMER_MODE_ABS);
+        ctx->moffs = ktime_get_monotonic_offset();
 
         ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx,
                                O_RDWR | (flags & TFD_SHARED_FCNTL_FLAGS));
@@ -199,6 +243,7 @@ SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
         struct file *file;
         struct timerfd_ctx *ctx;
         struct itimerspec ktmr, kotmr;
+        int ret;
 
         if (copy_from_user(&ktmr, utmr, sizeof(ktmr)))
                 return -EFAULT;
@@ -240,14 +285,14 @@ SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
         /*
          * Re-program the timer to the new value ...
          */
-        timerfd_setup(ctx, flags, &ktmr);
+        ret = timerfd_setup(ctx, flags, &ktmr);
 
         spin_unlock_irq(&ctx->wqh.lock);
         fput(file);
         if (otmr && copy_to_user(otmr, &kotmr, sizeof(kotmr)))
                 return -EFAULT;
 
-        return 0;
+        return ret;
 }
 
 SYSCALL_DEFINE2(timerfd_gettime, int, ufd, struct itimerspec __user *, otmr)
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 4135c88fe4fa..eda4ccde0730 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -155,6 +155,7 @@ enum  hrtimer_base_type {
         HRTIMER_BASE_REALTIME,
         HRTIMER_BASE_MONOTONIC,
         HRTIMER_BASE_BOOTTIME,
+        HRTIMER_BASE_REALTIME_COS,
         HRTIMER_MAX_CLOCK_BASES,
 };
 
@@ -310,6 +311,7 @@ extern void hrtimers_resume(void);
 extern ktime_t ktime_get(void);
 extern ktime_t ktime_get_real(void);
 extern ktime_t ktime_get_boottime(void);
+extern ktime_t ktime_get_monotonic_offset(void);
 
 DECLARE_PER_CPU(struct tick_device, tick_cpu_device);
 
diff --git a/include/linux/time.h b/include/linux/time.h
index b3061782dec3..a9242773eb24 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -302,6 +302,12 @@ struct itimerval {
  * The IDs of various hardware clocks:
  */
 #define CLOCK_SGI_CYCLE                 10
+
+#ifdef __KERNEL__
+/* This clock is not exposed to user space */
+#define CLOCK_REALTIME_COS              15
+#endif
+
 #define MAX_CLOCKS                      16
 #define CLOCKS_MASK                     (CLOCK_REALTIME | CLOCK_MONOTONIC)
 #define CLOCKS_MONO                     CLOCK_MONOTONIC
diff --git a/include/linux/timerfd.h b/include/linux/timerfd.h
index 2d0792983f8c..e9571fc8f1a0 100644
--- a/include/linux/timerfd.h
+++ b/include/linux/timerfd.h
@@ -19,6 +19,7 @@
  * shared O_* flags.
  */
 #define TFD_TIMER_ABSTIME (1 << 0)
+#define TFD_TIMER_CANCELON_SET (1 << 1)
 #define TFD_CLOEXEC O_CLOEXEC
 #define TFD_NONBLOCK O_NONBLOCK
 
@@ -26,6 +27,6 @@
 /* Flags for timerfd_create.  */
 #define TFD_CREATE_FLAGS TFD_SHARED_FCNTL_FLAGS
 /* Flags for timerfd_settime.  */
-#define TFD_SETTIME_FLAGS TFD_TIMER_ABSTIME
+#define TFD_SETTIME_FLAGS (TFD_TIMER_ABSTIME | TFD_TIMER_CANCELON_SET)
 
 #endif /* _LINUX_TIMERFD_H */
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index c145ed643bca..eabcbd781433 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -78,6 +78,11 @@ DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =
                         .get_time = &ktime_get_boottime,
                         .resolution = KTIME_LOW_RES,
                 },
+                {
+                        .index = CLOCK_REALTIME_COS,
+                        .get_time = &ktime_get_real,
+                        .resolution = KTIME_LOW_RES,
+                },
         }
 };
 
@@ -85,6 +90,7 @@ static const int hrtimer_clock_to_base_table[MAX_CLOCKS] = {
         [CLOCK_REALTIME]        = HRTIMER_BASE_REALTIME,
         [CLOCK_MONOTONIC]       = HRTIMER_BASE_MONOTONIC,
         [CLOCK_BOOTTIME]        = HRTIMER_BASE_BOOTTIME,
+        [CLOCK_REALTIME_COS]    = HRTIMER_BASE_REALTIME_COS,
 };
 
 static inline int hrtimer_clockid_to_base(clockid_t clock_id)
@@ -110,6 +116,7 @@ static void hrtimer_get_softirq_time(struct hrtimer_cpu_base *base)
         base->clock_base[HRTIMER_BASE_REALTIME].softirq_time = xtim;
         base->clock_base[HRTIMER_BASE_MONOTONIC].softirq_time = mono;
         base->clock_base[HRTIMER_BASE_BOOTTIME].softirq_time = boot;
+        base->clock_base[HRTIMER_BASE_REALTIME_COS].softirq_time = xtim;
 }
 
 /*
@@ -479,6 +486,8 @@ static inline void debug_deactivate(struct hrtimer *timer)
         trace_hrtimer_cancel(timer);
 }
 
+static void hrtimer_expire_cancelable(struct hrtimer_cpu_base *cpu_base);
+
 /* High resolution timer related functions */
 #ifdef CONFIG_HIGH_RES_TIMERS
 
@@ -715,9 +724,14 @@ static void retrigger_next_event(void *arg)
         struct hrtimer_cpu_base *base = &__get_cpu_var(hrtimer_bases);
         struct timespec realtime_offset, xtim, wtm, sleep;
 
-        if (!hrtimer_hres_active())
+        if (!hrtimer_hres_active()) {
+                raw_spin_lock(&base->lock);
+                hrtimer_expire_cancelable(base);
+                raw_spin_unlock(&base->lock);
                 return;
+        }
 
+        /* Optimized out for !HIGH_RES */
         get_xtime_and_monotonic_and_sleep_offset(&xtim, &wtm, &sleep);
         set_normalized_timespec(&realtime_offset, -wtm.tv_sec, -wtm.tv_nsec);
 
@@ -727,6 +741,10 @@ static void retrigger_next_event(void *arg)
                 timespec_to_ktime(realtime_offset);
         base->clock_base[HRTIMER_BASE_BOOTTIME].offset =
                 timespec_to_ktime(sleep);
+        base->clock_base[HRTIMER_BASE_REALTIME_COS].offset =
+                timespec_to_ktime(realtime_offset);
+
+        hrtimer_expire_cancelable(base);
 
         hrtimer_force_reprogram(base, 0);
         raw_spin_unlock(&base->lock);
@@ -1222,6 +1240,22 @@ static void __run_hrtimer(struct hrtimer *timer, ktime_t *now)
         timer->state &= ~HRTIMER_STATE_CALLBACK;
 }
 
+static void hrtimer_expire_cancelable(struct hrtimer_cpu_base *cpu_base)
+{
+        struct timerqueue_node *node;
+        struct hrtimer_clock_base *base;
+        ktime_t now = ktime_get_real();
+
+        base = &cpu_base->clock_base[HRTIMER_BASE_REALTIME_COS];
+
+        while ((node = timerqueue_getnext(&base->active))) {
+                        struct hrtimer *timer;
+
+                        timer = container_of(node, struct hrtimer, node);
+                        __run_hrtimer(timer, &now);
+        }
+}
+
 #ifdef CONFIG_HIGH_RES_TIMERS
 
 /*
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index a61b8fa2d39a..342408cf68dd 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1099,6 +1099,21 @@ void get_xtime_and_monotonic_and_sleep_offset(struct timespec *xtim,
 }
 
 /**
+ * ktime_get_monotonic_offset() - get wall_to_monotonic in ktime_t format
+ */
+ktime_t ktime_get_monotonic_offset(void)
+{
+        unsigned long seq;
+        struct timespec wtom;
+
+        do {
+                seq = read_seqbegin(&xtime_lock);
+                wtom = wall_to_monotonic;
+        } while (read_seqretry(&xtime_lock, seq));
+        return timespec_to_ktime(wtom);
+}
+
+/**
  * xtime_update() - advances the timekeeping infrastructure
  * @ticks:      number of ticks, that have elapsed since the last call.
  *