linux/kernel/time/timer.c, branch v4.15

timers: Unconditionally check deferrable base

2018-01-14T22:25:33Z

When the timer base is checked for expired timers then the deferrable base must be checked as well. This was missed when making the deferrable base independent of base::nohz_active. Fixes: ced6d5c11d3e ("timers: Use deferrable base independent of base::nohz_active") Signed-off-by: Thomas Gleixner Cc: Anna-Maria Gleixner Cc: Frederic Weisbecker Cc: Peter Zijlstra Cc: Sebastian Siewior Cc: Paul McKenney Cc: stable@vger.kernel.org Cc: rt@linutronix.de

timers: Invoke timer_start_debug() where it makes sense

2017-12-29T22:13:10Z

The timer start debug function is called before the proper timer base is set. As a consequence the trace data contains the stale CPU and flags values. Call the debug function after setting the new base and flags. Fixes: 500462a9de65 ("timers: Switch to a non-cascading wheel") Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: Frederic Weisbecker Cc: Sebastian Siewior Cc: stable@vger.kernel.org Cc: rt@linutronix.de Cc: Paul McKenney Cc: Anna-Maria Gleixner Link: https://lkml.kernel.org/r/20171222145337.792907137@linutronix.de

timers: Reinitialize per cpu bases on hotplug

2017-12-29T22:13:09Z

The timer wheel bases are not (re)initialized on CPU hotplug. That leaves them with a potentially stale clk and next_expiry valuem, which can cause trouble then the CPU is plugged. Add a prepare callback which forwards the clock, sets next_expiry to far in the future and reset the control flags to a known state. Set base->must_forward_clk so the first timer which is queued will try to forward the clock to current jiffies. Fixes: 500462a9de65 ("timers: Switch to a non-cascading wheel") Reported-by: Paul E. McKenney Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: Frederic Weisbecker Cc: Sebastian Siewior Cc: Anna-Maria Gleixner Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1712272152200.2431@nanos

timers: Use deferrable base independent of base::nohz_active

2017-12-29T22:13:09Z

During boot and before base::nohz_active is set in the timer bases, deferrable timers are enqueued into the standard timer base. This works correctly as long as base::nohz_active is false. Once it base::nohz_active is set and a timer which was enqueued before that is accessed the lock selector code choses the lock of the deferred base. This causes unlocked access to the standard base and in case the timer is removed it does not clear the pending flag in the standard base bitmap which causes get_next_timer_interrupt() to return bogus values. To prevent that, the deferrable timers must be enqueued in the deferrable base, even when base::nohz_active is not set. Those deferrable timers also need to be expired unconditional. Fixes: 500462a9de65 ("timers: Switch to a non-cascading wheel") Signed-off-by: Anna-Maria Gleixner Signed-off-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker Cc: Peter Zijlstra Cc: Sebastian Siewior Cc: stable@vger.kernel.org Cc: rt@linutronix.de Cc: Paul McKenney Link: https://lkml.kernel.org/r/20171222145337.633328378@linutronix.de

timer: Pass function down to initialization routines

2017-11-21T23:57:14Z

In preparation for removing more macros, pass the function down to the initialization routines instead of doing it in macros. Cc: Thomas Gleixner Cc: John Stultz Cc: Stephen Boyd Signed-off-by: Kees Cook

timer: Switch callback prototype to take struct timer_list * argument

2017-11-21T23:57:13Z

Since all callbacks have been converted, we can switch the core prototype to "struct timer_list *" now too. Cc: Thomas Gleixner Cc: John Stultz Cc: Stephen Boyd Signed-off-by: Kees Cook

timer: Pass timer_list pointer to callbacks unconditionally

2017-11-21T23:57:12Z

Now that all timer callbacks are already taking their struct timer_list pointer as the callback argument, just do this unconditionally and remove the .data field. Cc: Thomas Gleixner Cc: John Stultz Cc: Stephen Boyd Signed-off-by: Kees Cook

timers: Add a function to start/reduce a timer

2017-11-12T14:10:27Z

Add a function, similar to mod_timer(), that will start a timer if it isn't running and will modify it if it is running and has an expiry time longer than the new time. If the timer is running with an expiry time that's the same or sooner, no change is made. The function looks like: int timer_reduce(struct timer_list *timer, unsigned long expires); This can be used by code such as networking code to make it easier to share a timer for multiple timeouts. For instance, in upcoming AF_RXRPC code, the rxrpc_call struct will maintain a number of timeouts: unsigned long ack_at; unsigned long resend_at; unsigned long ping_at; unsigned long expect_rx_by; unsigned long expect_req_by; unsigned long expect_term_by; each of which is set independently of the others. With timer reduction available, when the code needs to set one of the timeouts, it only needs to look at that timeout and then call timer_reduce() to modify the timer, starting it or bringing it forward if necessary. There is no need to refer to the other timeouts to see which is earliest and no need to take any lock other than, potentially, the timer lock inside timer_reduce(). Note, that this does not protect against concurrent invocations of any of the timer functions. As an example, the expect_rx_by timeout above, which terminates a call if we don't get a packet from the server within a certain time window, would be set something like this: unsigned long now = jiffies; unsigned long expect_rx_by = now + packet_receive_timeout; WRITE_ONCE(call->expect_rx_by, expect_rx_by); timer_reduce(&call->timer, expect_rx_by); The timer service code (which might, say, be in a work function) would then check all the timeouts to see which, if any, had triggered, deal with those: t = READ_ONCE(call->ack_at); if (time_after_eq(now, t)) { cmpxchg(&call->ack_at, t, now + MAX_JIFFY_OFFSET); set_bit(RXRPC_CALL_EV_ACK, &call->events); } and then restart the timer if necessary by finding the soonest timeout that hasn't yet passed and then calling timer_reduce(). The disadvantage of doing things this way rather than comparing the timers each time and calling mod_timer() is that you *will* take timer events unless you can finish what you're doing and delete the timer in time. The advantage of doing things this way is that you don't need to use a lock to work out when the next timer should be set, other than the timer's own lock - which you might not have to take. [ tglx: Fixed weird formatting and adopted it to pending changes ] Signed-off-by: David Howells Signed-off-by: Thomas Gleixner Cc: keyrings@vger.kernel.org Cc: linux-afs@lists.infradead.org Link: https://lkml.kernel.org/r/151023090769.23050.1801643667223880753.stgit@warthog.procyon.org.uk

timer: Convert stub timer to timer_setup()

2017-10-18T15:04:25Z

In preparation for unconditionally passing the struct timer_list pointer to all timer callbacks, switch to using the new timer_setup() and from_timer() to pass the timer pointer explicitly. Signed-off-by: Thomas Gleixner Cc: Kees Cook

timers: Avoid an unnecessary iteration in __run_timers()

2017-10-18T13:29:33Z

If the base clock is behind jiffies in the soft irq expiry code then the next timer is retrieved by get_next_timer_interrupt() to avoid incrementing base clock one by one. If the next timer interrupt is past current jiffies then the base clock is set to jiffies - 1. At the call site this is incremented and another iteration through the expiry loop is executed which checks empty hash buckets. That's a pointless excercise because it's already known that the next timer is past jiffies. Set the base clock in that case to jiffies directly so it gets incremented to jiffies + 1 at the call site resulting in immediate termination of the expiry loop. [ tglx: Massaged changelog and added comment to the code ] Signed-off-by: Zhenzhong Duan Signed-off-by: Thomas Gleixner Acked-by: Anna-Maria Gleixner Cc: Joe Jin Cc: sboyd@codeaurora.org Cc: Srinivas Reddy Eeda Cc: john.stultz@linaro.org Link: https://lkml.kernel.org/r/7086a857-f90c-4616-bbe8-f7696f21626c@default