- 07 May, 2015 1 commit
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Thomas Gleixner authored
Simon Horman reported this crash on a system with high-res timers disabled but nohz enabled: > ------------[ cut here ]------------ > kernel BUG at kernel/irq_work.c:135! BUG_ON(!irqs_disabled()); So something enabled interrupts in the periodic tick handling machinery, and that code path indeed has a local_irq_disable()/enable pair in tick_nohz_switch_to_nohz() which causes havoc. Fix it. This patch also fixes a +nohz -hrtimers hang reported by Ingo Molnar. Reported-by:Simon Horman <horms@verge.net.au> Reported-by:
Ingo Molnar <mingo@kernel.org> Tested-by:
Thomas Gleixner <tglx@linutronix.de> Cc: Borislav Petkov <bp@alien8.de> Cc: H. Peter Anvin <hpa@zytor.com> Cc: LAK <linux-arm-kernel@lists.infradead.org> Cc: Magnus Damm <magnus.damm@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1505071425520.4225@nanosSigned-off-by:
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- 05 May, 2015 8 commits
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Andreas Sandberg authored
The hrtimer callback in the hrtimer's tick broadcast code sometimes incorrectly ends up scheduling events at the current tick causing the kernel to hang servicing the same hrtimer forever. This typically happens when a device is swapped out by tick_install_broadcast_device(), which replaces the event handler with clock_events_handle_noop() and sets the device mode to CLOCK_EVT_MODE_UNUSED. If the timer is scheduled when this happens, the next_event field will not be updated and the hrtimer ends up being restarted at the current tick. To prevent this from happening, only try to restart the hrtimer if the broadcast clock event device is in one of the active modes and try to cancel the timer when entering the CLOCK_EVT_MODE_UNUSED mode. Signed-off-by:
Andreas Sandberg <andreas.sandberg@arm.com> Tested-by:
Catalin Marinas <catalin.marinas@arm.com> Acked-by:
Mark Rutland <mark.rutland@arm.com> Reviewed-by:
Preeti U Murthy <preeti@linux.vnet.ibm.com> Link: http://lkml.kernel.org/r/1429880765-5558-1-git-send-email-andreas.sandberg@arm.comSigned-off-by:
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Joonwoo Park authored
At present, internal_add_timer() examines flags with 'base' which doesn't contain flags. Examine with 'timer->base' to avoid unnecessary waking up of nohz CPU when timer base has TIMER_DEFERRABLE set. Signed-off-by:
Joonwoo Park <joonwoop@codeaurora.org> Cc: sboyd@codeaurora.org Cc: skannan@codeaurora.org Cc: John Stultz <john.stultz@linaro.org> Link: http://lkml.kernel.org/r/1430187709-21087-1-git-send-email-joonwoop@codeaurora.orgSigned-off-by:
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Maxime Ripard authored
of_io_request_and map returns an error pointer, but the current code assumes that on error the returned pointer will be NULL. Obviously, that makes the check completely useless. Change the test to actually check for the proper error code. Signed-off-by:
Maxime Ripard <maxime.ripard@free-electrons.com> Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Link: http://lkml.kernel.org/r/1430579006-32702-6-git-send-email-maxime.ripard@free-electrons.comSigned-off-by:
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Maxime Ripard authored
of_io_request_and map returns an error pointer, but the current code assumes that on error the returned pointer will be NULL. Obviously, that makes the check completely useless. Change the test to actually check for the proper error code. Signed-off-by:
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Maxime Ripard authored
of_io_request_and map returns an error pointer, but the current code assumes that on error the returned pointer will be NULL. Obviously, that makes the check completely useless. Change the test to actually check for the proper error code. Signed-off-by:
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Preeti U Murthy authored
Today the number of bits of the broadcast masks that is output into /proc/timer_list is sizeof(unsigned long). This means that on machines with a larger number of CPUs, the bitmasks of CPUs beyond this range do not appear. Fix this by using bitmap printing through "%*pb" instead, so as to output the broadcast masks for the range of nr_cpu_ids into /proc/timer_list. Signed-off-by:
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Thomas Gleixner authored
Simplify the oneshot logic by avoiding the reprogramming loops. That also allows to call the cpu local handler outside of the broadcast_lock held region. Tested-by:
Borislav Petkov <bp@alien8.de> Signed-off-by:
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Thomas Gleixner authored
With the removal of the hrtimer softirq the switch to highres/nohz mode happens in the tick interrupt. That leads to a livelock when the per cpu event handler is directly called from the broadcast handler under broadcast lock because broadcast lock needs to be taken for the highres/nohz switch as well. Solve this by calling the cpu local handler outside the broadcast_lock held region. Fixes: c6eb3f70 "hrtimer: Get rid of hrtimer softirq" Reported-and-tested-by:
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- 04 May, 2015 1 commit
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Thomas Gleixner authored
Reported-by:
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- 23 Apr, 2015 2 commits
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Thomas Gleixner authored
The return value of hrtimer_start() tells whether the timer was inactive or active already when hrtimer_start() was called. The code emits a bogus warning if the timer was active already claiming that the timer could not be started. Remove it along with the bogus comment in the else path. Signed-off-by:
Frans Klaver <frans.klaver@xsens.com> Cc: Sebastian Reichel <sre@kernel.org> Cc: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Wolfram Sang <wsa@the-dreams.de> Cc: linux-pm@vger.kernel.org
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Thomas Gleixner authored
The struct member is gone. Reported-by: fengguang.wu@intel.com> Signed-off-by:
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- 22 Apr, 2015 28 commits
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kbuild test robot authored
Signed-off-by:
Fengguang Wu <fengguang.wu@intel.com> Cc: kbuild-all@01.org Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20150422200000.GA122603@lkp-sb04Signed-off-by:
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Peter Zijlstra authored
Thomas stumbled over the hrtimer_forward_now() in perf_event_mux_interval_ms_store() and noticed its broken-ness. You cannot just change the expiry time of an active timer, it will destroy the red-black tree order and cause havoc. Change it to (re)start the timer instead, (re)starting a timer will dequeue and enqueue a timer and therefore preserve rb-tree order. Since we cannot enqueue remotely, wrap the thing in cpu_function_call(), this however mandates that we restrict ourselves to online cpus. Also serialize the entire setting so we don't get multiple concurrent threads trying to update to different values. Also fix a problem in perf_mux_hrtimer_restart(), checking against hrtimer_active() can actually loose us the timer when timer->state == HRTIMER_STATE_CALLBACK and the callback has already decided NORESTART. Furthermore it doesn't make any sense to test hrtimer_callback_running() when we already tested hrtimer_active(), but with the above change, we explicitly must call it when callback_running. Lastly, rename a few functions: s/perf_cpu_hrtimer_/perf_mux_hrtimer_/ -- because I could not find the mux timer function s/\<hr\>/timer/ -- because that's the normal way of calling things. Fixes: 62b85639 ("perf: Add sysfs entry to adjust multiplexing interval per PMU") Reported-by:Peter Zijlstra (Intel) <peterz@infradead.org> Link: http://lkml.kernel.org/r/20150415095011.863052571@infradead.orgSigned-off-by:
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Peter Zijlstra authored
Roman reported a 3 cpu lockup scenario involving __start_cfs_bandwidth(). The more I look at that code the more I'm convinced its crack, that entire __start_cfs_bandwidth() thing is brain melting, we don't need to cancel a timer before starting it, *hrtimer_start*() will happily remove the timer for you if its still enqueued. Removing that, removes a big part of the problem, no more ugly cancel loop to get stuck in. So now, if I understand things right, the entire reason you have this cfs_b->lock guarded ->timer_active nonsense is to make sure we don't accidentally lose the timer. It appears to me that it should be possible to guarantee that same by unconditionally (re)starting the timer when !queued. Because regardless what hrtimer::function will return, if we beat it to (re)enqueue the timer, it doesn't matter. Now, because hrtimers don't come with any serialization guarantees we must ensure both handler and (re)start loop serialize their access to the hrtimer to avoid both trying to forward the timer at the same time. Update the rt bandwidth timer to match. This effectively reverts: 09dc4ab0 ("sched/fair: Fix tg_set_cfs_bandwidth() deadlock on rq->lock"). Reported-by:
Roman Gushchin <klamm@yandex-team.ru> Signed-off-by:
Ben Segall <bsegall@google.com> Cc: Paul Turner <pjt@google.com> Link: http://lkml.kernel.org/r/20150415095011.804589208@infradead.orgSigned-off-by:
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Peter Zijlstra authored
Because we drop cpu_base->lock around calling hrtimer::function, it is possible for hrtimer_start() to come in between and enqueue the timer. If hrtimer::function then returns HRTIMER_RESTART we'll hit the BUG_ON because HRTIMER_STATE_ENQUEUED will be set. Since the above is a perfectly valid scenario, remove the BUG_ON and make the enqueue_hrtimer() call conditional on the timer not being enqueued already. NOTE: in that concurrent scenario its entirely common for both sites to want to modify the hrtimer, since hrtimers don't provide serialization themselves be sure to provide some such that the hrtimer::function and the hrtimer_start() caller don't both try and fudge the expiration state at the same time. To that effect, add a WARN when someone tries to forward an already enqueued timer, the most common way to change the expiry of self restarting timers. Ideally we'd put the WARN in everything modifying the expiry but most of that is inlines and we don't need the bloat. Fixes: 2d44ae4d ("hrtimer: clean up cpu->base locking tricks") Signed-off-by:
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Thomas Gleixner authored
do_usleep_range() and schedule_hrtimeout_range() are __sched as well. So it makes no sense to have the exported function in a different section. Signed-off-by:
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Thomas Gleixner authored
The only user ignores it anyway and rightfully so. Signed-off-by:
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Thomas Gleixner authored
We can do a lockless check for hrtimer_active before actually taking the lock in hrtimer[_try_to]_cancel. This is useful for hotpath users like nanosleep as they avoid the lock dance when the timer has expired. This is safe because active is true when the timer is enqueued or the callback is running. Taking the hrtimer base lock does not protect against concurrent hrtimer_start calls, the callsite has to do the proper serialization itself. Signed-off-by:
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Thomas Gleixner authored
No user was ever interested whether the timer was active or not when it was started. All abusers of the return value are gone, so get rid of it. Signed-off-by:
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Thomas Gleixner authored
The assignment of bc_moved in the conditional construct relies on the fact that in the case of hrtimer_start() invocation the return value is always 0. It took me a while to understand it. We want to get rid of the hrtimer_start() return value. Open code the logic which makes it readable as well. Signed-off-by:
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Thomas Gleixner authored
We want to get rid of the hrtimer_start() return value and the alarm timer return value is nowhere used. Remove it. Signed-off-by:
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Thomas Gleixner authored
The check for hrtimer_active() after starting the timer is pointless. If the timer is inactive it has expired already and therefor the task pointer is already NULL. Signed-off-by:
David S. Miller <davem@davemloft.net> Link: http://lkml.kernel.org/r/20150414203503.165258315@linutronix.deSigned-off-by:
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Thomas Gleixner authored
The check for hrtimer_active() after starting the timer is pointless. If the timer is inactive it has expired already and therefor the task pointer is already NULL. Signed-off-by:
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Thomas Gleixner authored
The check for hrtimer_active() after starting the timer is pointless. If the timer is inactive it has expired already and therefor the task pointer is already NULL. Signed-off-by:
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Thomas Gleixner authored
The check for hrtimer_active() after starting the timer is pointless. If the timer is inactive it has expired already and therefor the task pointer is already NULL. Signed-off-by:
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Thomas Gleixner authored
No point for an extra export just to set the extra argument of hrtimer_start_range_ns() to 0. Signed-off-by:
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Thomas Gleixner authored
No more callers. Remove the leftovers. Signed-off-by:
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Thomas Gleixner authored
hrtimer_start() does not longer defer already expired timers to the softirq. Get rid of the __hrtimer_start_range_ns() invocation. Signed-off-by:
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Thomas Gleixner authored
hrtimer_start() now enforces a timer interrupt when an already expired timer is enqueued. Get rid of the __hrtimer_start_range_ns() invocations and the loops around it. Signed-off-by:
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Thomas Gleixner authored
hrtimer_start() does not longer defer already expired timers to the softirq. Get rid of the __hrtimer_start_range_ns() invocation. Signed-off-by:
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Thomas Gleixner authored
hrtimer_start() does not longer defer already expired timers to the softirq. Get rid of the __hrtimer_start_range_ns() invocation. Signed-off-by:
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Thomas Gleixner authored
hrtimer_start() does not longer defer already expired timers to the softirq. Get rid of the __hrtimer_start_range_ns() invocation. Signed-off-by:
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Thomas Gleixner authored
The evaluation of the next timer in the nohz code is based on jiffies while all the tick internals are nano seconds based. We have also to convert hrtimer nanoseconds to jiffies in the !highres case. That's just wrong and introduces interesting corner cases. Turn it around and convert the next timer wheel timer expiry and the rcu event to clock monotonic and base all calculations on nanoseconds. That identifies the case where no timer is pending clearly with an absolute expiry value of KTIME_MAX. Makes the code more readable and gets rid of the jiffies magic in the nohz code. Signed-off-by:
Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by:
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Thomas Gleixner authored
Get rid of one indentation level. Preparatory patch for a major rework. No functional change. Signed-off-by:
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Thomas Gleixner authored
We already got rid of the hrtimer reprogramming loops and hoops as hrtimer now enforces an interrupt if the enqueued time is in the past. Do the same for the nohz non highres mode. That gets rid of the need to raise the softirq which only serves the purpose of getting the machine out of the inner idle loop. Signed-off-by:
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Thomas Gleixner authored
hrtimer_start() enforces a timer interrupt if the timer is already expired. Get rid of the checks and the forward loop. Signed-off-by:
Frederic Weisbecker <fweisbec@gmail.com> Acked-by:
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Thomas Gleixner authored
hrtimer softirq is a leftover from the initial implementation and serves only the purpose to handle the enqueueing of already expired timers in the high resolution timer mode. We discussed whether we change the return value and force all start sites to handle that the timer is already expired, but that would be a Herculean task and I'm not sure whether its a good idea to enforce that handling on everyone. A simpler solution is to enforce a timer interrupt instead of raising and scheduling a softirq. Just use the existing infrastructure to do so and remove all the softirq leftovers. The HRTIMER softirq enum is now unused, but kept around because trace parsers rely on the existing numbering. Signed-off-by:
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Thomas Gleixner authored
__remove_hrtimer() needs to evaluate the expiry time to figure out whether the timer which is removed is eventually the first expiring timer on the cpu. Keep a pointer to it, which is lazily updated, so we can avoid the evaluation dance and retrieve the information from there. Generates slightly better code. Signed-off-by:
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Thomas Gleixner authored
Use the return value instead of reevaluating the information. Signed-off-by:
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