user/sven/linux.git/kernel, branch v4.14.4

genirq: Track whether the trigger type has been set

2017-11-30T08:40:52Z

commit 4f8413a3a799c958f7a10a6310a451e6b8aef5ad upstream. When requesting a shared interrupt, we assume that the firmware support code (DT or ACPI) has called irqd_set_trigger_type already, so that we can retrieve it and check that the requester is being reasonnable. Unfortunately, we still have non-DT, non-ACPI systems around, and these guys won't call irqd_set_trigger_type before requesting the interrupt. The consequence is that we fail the request that would have worked before. We can either chase all these use cases (boring), or address it in core code (easier). Let's have a per-irq_desc flag that indicates whether irqd_set_trigger_type has been called, and let's just check it when checking for a shared interrupt. If it hasn't been set, just take whatever the interrupt requester asks. Fixes: 382bd4de6182 ("genirq: Use irqd_get_trigger_type to compare the trigger type for shared IRQs") Reported-and-tested-by: Petr Cvek Signed-off-by: Marc Zyngier Signed-off-by: Greg Kroah-Hartman

sched/rt: Simplify the IPI based RT balancing logic

2017-11-30T08:40:43Z

commit 4bdced5c9a2922521e325896a7bbbf0132c94e56 upstream. When a CPU lowers its priority (schedules out a high priority task for a lower priority one), a check is made to see if any other CPU has overloaded RT tasks (more than one). It checks the rto_mask to determine this and if so it will request to pull one of those tasks to itself if the non running RT task is of higher priority than the new priority of the next task to run on the current CPU. When we deal with large number of CPUs, the original pull logic suffered from large lock contention on a single CPU run queue, which caused a huge latency across all CPUs. This was caused by only having one CPU having overloaded RT tasks and a bunch of other CPUs lowering their priority. To solve this issue, commit: b6366f048e0c ("sched/rt: Use IPI to trigger RT task push migration instead of pulling") changed the way to request a pull. Instead of grabbing the lock of the overloaded CPU's runqueue, it simply sent an IPI to that CPU to do the work. Although the IPI logic worked very well in removing the large latency build up, it still could suffer from a large number of IPIs being sent to a single CPU. On a 80 CPU box, I measured over 200us of processing IPIs. Worse yet, when I tested this on a 120 CPU box, with a stress test that had lots of RT tasks scheduling on all CPUs, it actually triggered the hard lockup detector! One CPU had so many IPIs sent to it, and due to the restart mechanism that is triggered when the source run queue has a priority status change, the CPU spent minutes! processing the IPIs. Thinking about this further, I realized there's no reason for each run queue to send its own IPI. As all CPUs with overloaded tasks must be scanned regardless if there's one or many CPUs lowering their priority, because there's no current way to find the CPU with the highest priority task that can schedule to one of these CPUs, there really only needs to be one IPI being sent around at a time. This greatly simplifies the code! The new approach is to have each root domain have its own irq work, as the rto_mask is per root domain. The root domain has the following fields attached to it: rto_push_work - the irq work to process each CPU set in rto_mask rto_lock - the lock to protect some of the other rto fields rto_loop_start - an atomic that keeps contention down on rto_lock the first CPU scheduling in a lower priority task is the one to kick off the process. rto_loop_next - an atomic that gets incremented for each CPU that schedules in a lower priority task. rto_loop - a variable protected by rto_lock that is used to compare against rto_loop_next rto_cpu - The cpu to send the next IPI to, also protected by the rto_lock. When a CPU schedules in a lower priority task and wants to make sure overloaded CPUs know about it. It increments the rto_loop_next. Then it atomically sets rto_loop_start with a cmpxchg. If the old value is not "0", then it is done, as another CPU is kicking off the IPI loop. If the old value is "0", then it will take the rto_lock to synchronize with a possible IPI being sent around to the overloaded CPUs. If rto_cpu is greater than or equal to nr_cpu_ids, then there's either no IPI being sent around, or one is about to finish. Then rto_cpu is set to the first CPU in rto_mask and an IPI is sent to that CPU. If there's no CPUs set in rto_mask, then there's nothing to be done. When the CPU receives the IPI, it will first try to push any RT tasks that is queued on the CPU but can't run because a higher priority RT task is currently running on that CPU. Then it takes the rto_lock and looks for the next CPU in the rto_mask. If it finds one, it simply sends an IPI to that CPU and the process continues. If there's no more CPUs in the rto_mask, then rto_loop is compared with rto_loop_next. If they match, everything is done and the process is over. If they do not match, then a CPU scheduled in a lower priority task as the IPI was being passed around, and the process needs to start again. The first CPU in rto_mask is sent the IPI. This change removes this duplication of work in the IPI logic, and greatly lowers the latency caused by the IPIs. This removed the lockup happening on the 120 CPU machine. It also simplifies the code tremendously. What else could anyone ask for? Thanks to Peter Zijlstra for simplifying the rto_loop_start atomic logic and supplying me with the rto_start_trylock() and rto_start_unlock() helper functions. Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Peter Zijlstra (Intel) Cc: Clark Williams Cc: Daniel Bristot de Oliveira Cc: John Kacur Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Scott Wood Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20170424114732.1aac6dc4@gandalf.local.home Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

sched: Make resched_cpu() unconditional

2017-11-30T08:40:39Z

commit 7c2102e56a3f7d85b5d8f33efbd7aecc1f36fdd8 upstream. The current implementation of synchronize_sched_expedited() incorrectly assumes that resched_cpu() is unconditional, which it is not. This means that synchronize_sched_expedited() can hang when resched_cpu()'s trylock fails as follows (analysis by Neeraj Upadhyay): o CPU1 is waiting for expedited wait to complete: sync_rcu_exp_select_cpus rdp->exp_dynticks_snap & 0x1 // returns 1 for CPU5 IPI sent to CPU5 synchronize_sched_expedited_wait ret = swait_event_timeout(rsp->expedited_wq, sync_rcu_preempt_exp_done(rnp_root), jiffies_stall); expmask = 0x20, CPU 5 in idle path (in cpuidle_enter()) o CPU5 handles IPI and fails to acquire rq lock. Handles IPI sync_sched_exp_handler resched_cpu returns while failing to try lock acquire rq->lock need_resched is not set o CPU5 calls rcu_idle_enter() and as need_resched is not set, goes to idle (schedule() is not called). o CPU 1 reports RCU stall. Given that resched_cpu() is now used only by RCU, this commit fixes the assumption by making resched_cpu() unconditional. Reported-by: Neeraj Upadhyay Suggested-by: Neeraj Upadhyay Signed-off-by: Paul E. McKenney Acked-by: Steven Rostedt (VMware) Acked-by: Peter Zijlstra (Intel) Signed-off-by: Greg Kroah-Hartman

cpufreq: schedutil: Reset cached_raw_freq when not in sync with next_freq

2017-11-30T08:40:39Z

commit 07458f6a5171d97511dfbdf6ce549ed2ca0280c7 upstream. 'cached_raw_freq' is used to get the next frequency quickly but should always be in sync with sg_policy->next_freq. There is a case where it is not and in such cases it should be reset to avoid switching to incorrect frequencies. Consider this case for example: - policy->cur is 1.2 GHz (Max) - New request comes for 780 MHz and we store that in cached_raw_freq. - Based on 780 MHz, we calculate the effective frequency as 800 MHz. - We then see the CPU wasn't idle recently and choose to keep the next freq as 1.2 GHz. - Now we have cached_raw_freq is 780 MHz and sg_policy->next_freq is 1.2 GHz. - Now if the utilization doesn't change in then next request, then the next target frequency will still be 780 MHz and it will match with cached_raw_freq. But we will choose 1.2 GHz instead of 800 MHz here. Fixes: b7eaf1aab9f8 (cpufreq: schedutil: Avoid reducing frequency of busy CPUs prematurely) Signed-off-by: Viresh Kumar Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman

rcu: Fix up pending cbs check in rcu_prepare_for_idle

2017-11-24T07:37:04Z

commit 135bd1a230bb69a68c9808a7d25467318900b80a upstream. The pending-callbacks check in rcu_prepare_for_idle() is backwards. It should accelerate if there are pending callbacks, but the check rather uselessly accelerates only if there are no callbacks. This commit therefore inverts this check. Fixes: 15fecf89e46a ("srcu: Abstract multi-tail callback list handling") Signed-off-by: Neeraj Upadhyay Signed-off-by: Paul E. McKenney Signed-off-by: Greg Kroah-Hartman

Merge tag 'pm-final-4.14' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

2017-11-09T19:16:28Z

Pull final power management fixes from Rafael Wysocki: "These fix a regression in the schedutil cpufreq governor introduced by a recent change and blacklist Dell XPS13 9360 from using the Low Power S0 Idle _DSM interface which triggers serious problems on one of these machines. Specifics: - Prevent the schedutil cpufreq governor from using the utilization of a wrong CPU in some cases which started to happen after one of the recent changes in it (Chris Redpath). - Blacklist Dell XPS13 9360 from using the Low Power S0 Idle _DSM interface as that causes serious issue (related to NVMe) to appear on one of these machines, even though the other Dells XPS13 9360 in somewhat different HW configurations behave correctly (Rafael Wysocki)" * tag 'pm-final-4.14' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: ACPI / PM: Blacklist Low Power S0 Idle _DSM for Dell XPS13 9360 cpufreq: schedutil: Examine the correct CPU when we update util

Merge branch 'pm-cpufreq-sched'

2017-11-08T23:07:56Z

* pm-cpufreq-sched: cpufreq: schedutil: Examine the correct CPU when we update util

Merge branch 'for-4.14-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq

2017-11-06T20:26:49Z

Pull workqueue fix from Tejun Heo: "Another fix for a really old bug. It only affects drain_workqueue() which isn't used often and even then triggers only during a pretty small race window, so it isn't too surprising that it stayed hidden for so long. The fix is straight-forward and low-risk. Kudos to Li Bin for reporting and fixing the bug" * 'for-4.14-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq: workqueue: Fix NULL pointer dereference

Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2017-11-05T19:44:39Z

Pull perf fixes from Ingo Molnar: "Various fixes: - synchronize kernel and tooling headers - cgroup support fix - two tooling fixes" * 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: tools/headers: Synchronize kernel ABI headers perf/cgroup: Fix perf cgroup hierarchy support perf tools: Unwind properly location after REJECT perf symbols: Fix memory corruption because of zero length symbols

cpufreq: schedutil: Examine the correct CPU when we update util

2017-11-04T16:44:28Z

After commit 674e75411fc2 (sched: cpufreq: Allow remote cpufreq callbacks) we stopped to always read the utilization for the CPU we are running the governor on, and instead we read it for the CPU which we've been told has updated utilization. This is stored in sugov_cpu->cpu. The value is set in sugov_register() but we clear it in sugov_start() which leads to always looking at the utilization of CPU0 instead of the correct one. Fix this by consolidating the initialization code into sugov_start(). Fixes: 674e75411fc2 (sched: cpufreq: Allow remote cpufreq callbacks) Signed-off-by: Chris Redpath Reviewed-by: Patrick Bellasi Reviewed-by: Brendan Jackman Acked-by: Viresh Kumar Signed-off-by: Rafael J. Wysocki