Messages in this thread | | | Date | Wed, 17 Nov 2010 12:42:52 -0800 (PST) | From | Davide Libenzi <> | Subject | Re: [PATCHv6 0/7] system time changes notification |
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On Wed, 17 Nov 2010, Alexander Shishkin wrote:
> > But what you folks really want for this stuff is an extension to > > timerfd as you want to be able to poll, right? > > > > So what about the following: > > > > Add a new flag TDF_NOTIFY_CLOCK_WAS_SET to the timerfd flags. Now this > > flag adds the timer to a separate list, which gets woken up when the > > clock is set. > > > > No new syscall, just a few lines of code in fs/timerfd.c and > > clock_was_set(). > > > > Thoughts ? > > Something like this (sans ugliness)?
Oh, gosh, please. This is interface-multiplexing-a-palooza. It should be decided if the feature makes sense, and then have proper interface, instead of multiplexing unrelated insterfaces. This is a sort of system-event-report pattern. What is wrong with using a netlink-based transport for those kind of things?
> Signed-off-by: Alexander Shishkin <virtuoso@slind.org> > --- > fs/timerfd.c | 52 +++++++++++++++++++++++++++++++++++++++++++++- > include/linux/timerfd.h | 3 +- > kernel/hrtimer.c | 2 + > 3 files changed, 54 insertions(+), 3 deletions(-) > > diff --git a/fs/timerfd.c b/fs/timerfd.c > index 8c4fc14..51a033e 100644 > --- a/fs/timerfd.c > +++ b/fs/timerfd.c > @@ -30,8 +30,14 @@ struct timerfd_ctx { > u64 ticks; > int expired; > int clockid; > + int clock_notifier; /* list_empty()? */ > + struct list_head notifiers_list; > }; > > +/* TFD_NOTIFY_CLOCK_SET timers go here */ > +static DEFINE_SPINLOCK(notifiers_lock); > +static LIST_HEAD(notifiers_list); > + > /* > * 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, > @@ -51,6 +57,21 @@ static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr) > return HRTIMER_NORESTART; > } > > +void timerfd_clock_was_set(void) > +{ > + struct timerfd_ctx *ctx; > + unsigned long flags; > + > + spin_lock(¬ifiers_lock); > + list_for_each_entry(ctx, ¬ifiers_list, notifiers_list) { > + spin_lock_irqsave(&ctx->wqh.lock, flags); > + ctx->ticks++; > + wake_up_locked(&ctx->wqh); > + spin_unlock_irqrestore(&ctx->wqh.lock, flags); > + } > + spin_unlock(¬ifiers_lock); > +} > + > static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx) > { > ktime_t remaining; > @@ -65,6 +86,14 @@ static void timerfd_setup(struct timerfd_ctx *ctx, int flags, > enum hrtimer_mode htmode; > ktime_t texp; > > + if (flags & TFD_NOTIFY_CLOCK_SET) { > + ctx->clock_notifier = 1; > + ctx->ticks = 0; > + INIT_LIST_HEAD(&ctx->notifiers_list); > + list_add(&ctx->notifiers_list, ¬ifiers_list); > + return; > + } > + > htmode = (flags & TFD_TIMER_ABSTIME) ? > HRTIMER_MODE_ABS: HRTIMER_MODE_REL; > > @@ -83,7 +112,12 @@ static int timerfd_release(struct inode *inode, struct file *file) > { > struct timerfd_ctx *ctx = file->private_data; > > - hrtimer_cancel(&ctx->tmr); > + if (ctx->clock_notifier) { > + spin_lock(¬ifiers_lock); > + list_del(&ctx->notifiers_list); > + spin_unlock(¬ifiers_lock); > + } else > + hrtimer_cancel(&ctx->tmr); > kfree(ctx); > return 0; > } > @@ -113,6 +147,7 @@ static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count, > > if (count < sizeof(ticks)) > return -EINVAL; > + > spin_lock_irq(&ctx->wqh.lock); > if (file->f_flags & O_NONBLOCK) > res = -EAGAIN; > @@ -120,7 +155,7 @@ static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count, > res = wait_event_interruptible_locked_irq(ctx->wqh, ctx->ticks); > if (ctx->ticks) { > ticks = ctx->ticks; > - if (ctx->expired && ctx->tintv.tv64) { > + if (ctx->expired && ctx->tintv.tv64 && !ctx->clock_notifier) { > /* > * If tintv.tv64 != 0, this is a periodic timer that > * needs to be re-armed. We avoid doing it in the timer > @@ -218,13 +253,20 @@ SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags, > * it to the new values. > */ > for (;;) { > + spin_lock(¬ifiers_lock); > spin_lock_irq(&ctx->wqh.lock); > if (hrtimer_try_to_cancel(&ctx->tmr) >= 0) > break; > spin_unlock_irq(&ctx->wqh.lock); > + spin_unlock(¬ifiers_lock); > cpu_relax(); > } > > + if (ctx->clock_notifier) { > + ctx->clock_notifier = 0; > + list_del(&ctx->notifiers_list); > + } > + > /* > * If the timer is expired and it's periodic, we need to advance it > * because the caller may want to know the previous expiration time. > @@ -243,6 +285,7 @@ SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags, > timerfd_setup(ctx, flags, &ktmr); > > spin_unlock_irq(&ctx->wqh.lock); > + spin_unlock(¬ifiers_lock); > fput(file); > if (otmr && copy_to_user(otmr, &kotmr, sizeof(kotmr))) > return -EFAULT; > @@ -262,6 +305,11 @@ SYSCALL_DEFINE2(timerfd_gettime, int, ufd, struct itimerspec __user *, otmr) > ctx = file->private_data; > > spin_lock_irq(&ctx->wqh.lock); > + if (ctx->clock_notifier) { > + spin_unlock_irq(&ctx->wqh.lock); > + return -EINVAL; > + } > + > if (ctx->expired && ctx->tintv.tv64) { > ctx->expired = 0; > ctx->ticks += > diff --git a/include/linux/timerfd.h b/include/linux/timerfd.h > index 2d07929..c3ddad9 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_NOTIFY_CLOCK_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_NOTIFY_CLOCK_SET) > > #endif /* _LINUX_TIMERFD_H */ > diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c > index 72206cf..a779e0f 100644 > --- a/kernel/hrtimer.c > +++ b/kernel/hrtimer.c > @@ -642,8 +642,10 @@ static void retrigger_next_event(void *arg) > * resolution timer interrupts. On UP we just disable interrupts and > * call the high resolution interrupt code. > */ > +void timerfd_clock_was_set(clockid_t clockid); > void clock_was_set(void) > { > + timerfd_clock_was_set(CLOCK_REALTIME); > /* Retrigger the CPU local events everywhere */ > on_each_cpu(retrigger_next_event, NULL, 1); > } > -- > 1.7.2.1.45.gb66c2 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
- Davide
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