user/sven/linux.git/kernel/sched, branch v4.14.72

sched/fair: Fix util_avg of new tasks for asymmetric systems

2018-09-26T06:38:12Z

[ Upstream commit 8fe5c5a937d0f4e84221631833a2718afde52285 ] When a new task wakes-up for the first time, its initial utilization is set to half of the spare capacity of its CPU. The current implementation of post_init_entity_util_avg() uses SCHED_CAPACITY_SCALE directly as a capacity reference. As a result, on a big.LITTLE system, a new task waking up on an idle little CPU will be given ~512 of util_avg, even if the CPU's capacity is significantly less than that. Fix this by computing the spare capacity with arch_scale_cpu_capacity(). Signed-off-by: Quentin Perret Signed-off-by: Peter Zijlstra (Intel) Acked-by: Vincent Guittot Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: dietmar.eggemann@arm.com Cc: morten.rasmussen@arm.com Cc: patrick.bellasi@arm.com Link: http://lkml.kernel.org/r/20180612112215.25448-1-quentin.perret@arm.com Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

sched/core: Use smp_mb() in wake_woken_function()

2018-09-26T06:38:10Z

[ Upstream commit 76e079fefc8f62bd9b2cd2950814d1ee806e31a5 ] wake_woken_function() synchronizes with wait_woken() as follows: [wait_woken] [wake_woken_function] entry->flags &= ~wq_flag_woken; condition = true; smp_mb(); smp_wmb(); if (condition) wq_entry->flags |= wq_flag_woken; break; This commit replaces the above smp_wmb() with an smp_mb() in order to guarantee that either wait_woken() sees the wait condition being true or the store to wq_entry->flags in woken_wake_function() follows the store in wait_woken() in the coherence order (so that the former can eventually be observed by wait_woken()). The commit also fixes a comment associated to set_current_state() in wait_woken(): the comment pairs the barrier in set_current_state() to the above smp_wmb(), while the actual pairing involves the barrier in set_current_state() and the barrier executed by the try_to_wake_up() in wake_woken_function(). Signed-off-by: Andrea Parri Signed-off-by: Paul E. McKenney Acked-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: akiyks@gmail.com Cc: boqun.feng@gmail.com Cc: dhowells@redhat.com Cc: j.alglave@ucl.ac.uk Cc: linux-arch@vger.kernel.org Cc: luc.maranget@inria.fr Cc: npiggin@gmail.com Cc: parri.andrea@gmail.com Cc: stern@rowland.harvard.edu Cc: will.deacon@arm.com Link: http://lkml.kernel.org/r/20180716180605.16115-10-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

sched/deadline: Fix switching to -deadline

2018-09-15T07:45:35Z

commit 295d6d5e373607729bcc8182c25afe964655714f upstream. Fix a bug introduced in: 72f9f3fdc928 ("sched/deadline: Remove dl_new from struct sched_dl_entity") After that commit, when switching to -deadline if the scheduling deadline of a task is in the past then switched_to_dl() calls setup_new_entity() to properly initialize the scheduling deadline and runtime. The problem is that the task is enqueued _before_ having its parameters initialized by setup_new_entity(), and this can cause problems. For example, a task with its out-of-date deadline in the past will potentially be enqueued as the highest priority one; however, its adjusted deadline may not be the earliest one. This patch fixes the problem by initializing the task's parameters before enqueuing it. Signed-off-by: luca abeni Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Daniel Bristot de Oliveira Cc: Juri Lelli Cc: Linus Torvalds Cc: Mathieu Poirier Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1504778971-13573-3-git-send-email-luca.abeni@santannapisa.it Signed-off-by: Ingo Molnar Signed-off-by: Sudip Mukherjee Signed-off-by: Greg Kroah-Hartman

sched/rt: Restore rt_runtime after disabling RT_RUNTIME_SHARE

2018-09-05T07:26:29Z

[ Upstream commit f3d133ee0a17d5694c6f21873eec9863e11fa423 ] NO_RT_RUNTIME_SHARE feature is used to prevent a CPU borrow enough runtime with a spin-rt-task. However, if RT_RUNTIME_SHARE feature is enabled and rt_rq has borrowd enough rt_runtime at the beginning, rt_runtime can't be restored to its initial bandwidth rt_runtime after we disable RT_RUNTIME_SHARE. E.g. on my PC with 4 cores, procedure to reproduce: 1) Make sure RT_RUNTIME_SHARE is enabled cat /sys/kernel/debug/sched_features GENTLE_FAIR_SLEEPERS START_DEBIT NO_NEXT_BUDDY LAST_BUDDY CACHE_HOT_BUDDY WAKEUP_PREEMPTION NO_HRTICK NO_DOUBLE_TICK LB_BIAS NONTASK_CAPACITY TTWU_QUEUE NO_SIS_AVG_CPU SIS_PROP NO_WARN_DOUBLE_CLOCK RT_PUSH_IPI RT_RUNTIME_SHARE NO_LB_MIN ATTACH_AGE_LOAD WA_IDLE WA_WEIGHT WA_BIAS 2) Start a spin-rt-task ./loop_rr & 3) set affinity to the last cpu taskset -p 8 $pid_of_loop_rr 4) Observe that last cpu have borrowed enough runtime. cat /proc/sched_debug | grep rt_runtime .rt_runtime : 950.000000 .rt_runtime : 900.000000 .rt_runtime : 950.000000 .rt_runtime : 1000.000000 5) Disable RT_RUNTIME_SHARE echo NO_RT_RUNTIME_SHARE > /sys/kernel/debug/sched_features 6) Observe that rt_runtime can not been restored cat /proc/sched_debug | grep rt_runtime .rt_runtime : 950.000000 .rt_runtime : 900.000000 .rt_runtime : 950.000000 .rt_runtime : 1000.000000 This patch help to restore rt_runtime after we disable RT_RUNTIME_SHARE. Signed-off-by: Hailong Liu Signed-off-by: Jiang Biao Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: zhong.weidong@zte.com.cn Link: http://lkml.kernel.org/r/1531874815-39357-1-git-send-email-liu.hailong6@zte.com.cn Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

sched/smt: Update sched_smt_present at runtime

2018-08-15T16:12:51Z

commit ba2591a5993eabcc8e874e30f361d8ffbb10d6d4 upstream The static key sched_smt_present is only updated at boot time when SMT siblings have been detected. Booting with maxcpus=1 and bringing the siblings online after boot rebuilds the scheduling domains correctly but does not update the static key, so the SMT code is not enabled. Let the key be updated in the scheduler CPU hotplug code to fix this. Signed-off-by: Peter Zijlstra Signed-off-by: Thomas Gleixner Reviewed-by: Konrad Rzeszutek Wilk Acked-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

sched/core: Require cpu_active() in select_task_rq(), for user tasks

2018-07-08T13:30:53Z

[ Upstream commit 7af443ee1697607541c6346c87385adab2214743 ] select_task_rq() is used in a few paths to select the CPU upon which a thread should be run - for example it is used by try_to_wake_up() & by fork or exec balancing. As-is it allows use of any online CPU that is present in the task's cpus_allowed mask. This presents a problem because there is a period whilst CPUs are brought online where a CPU is marked online, but is not yet fully initialized - ie. the period where CPUHP_AP_ONLINE_IDLE <= state < CPUHP_ONLINE. Usually we don't run any user tasks during this window, but there are corner cases where this can happen. An example observed is: - Some user task A, running on CPU X, forks to create task B. - sched_fork() calls __set_task_cpu() with cpu=X, setting task B's task_struct::cpu field to X. - CPU X is offlined. - Task A, currently somewhere between the __set_task_cpu() in copy_process() and the call to wake_up_new_task(), is migrated to CPU Y by migrate_tasks() when CPU X is offlined. - CPU X is onlined, but still in the CPUHP_AP_ONLINE_IDLE state. The scheduler is now active on CPU X, but there are no user tasks on the runqueue. - Task A runs on CPU Y & reaches wake_up_new_task(). This calls select_task_rq() with cpu=X, taken from task B's task_struct, and select_task_rq() allows CPU X to be returned. - Task A enqueues task B on CPU X's runqueue, via activate_task() & enqueue_task(). - CPU X now has a user task on its runqueue before it has reached the CPUHP_ONLINE state. In most cases, the user tasks that schedule on the newly onlined CPU have no idea that anything went wrong, but one case observed to be problematic is if the task goes on to invoke the sched_setaffinity syscall. The newly onlined CPU reaches the CPUHP_AP_ONLINE_IDLE state before the CPU that brought it online calls stop_machine_unpark(). This means that for a portion of the window of time between CPUHP_AP_ONLINE_IDLE & CPUHP_ONLINE the newly onlined CPU's struct cpu_stopper has its enabled field set to false. If a user thread is executed on the CPU during this window and it invokes sched_setaffinity with a CPU mask that does not include the CPU it's running on, then when __set_cpus_allowed_ptr() calls stop_one_cpu() intending to invoke migration_cpu_stop() and perform the actual migration away from the CPU it will simply return -ENOENT rather than calling migration_cpu_stop(). We then return from the sched_setaffinity syscall back to the user task that is now running on a CPU which it just asked not to run on, and which is not present in its cpus_allowed mask. This patch resolves the problem by having select_task_rq() enforce that user tasks run on CPUs that are active - the same requirement that select_fallback_rq() already enforces. This should ensure that newly onlined CPUs reach the CPUHP_AP_ACTIVE state before being able to schedule user tasks, and also implies that bringup_wait_for_ap() will have called stop_machine_unpark() which resolves the sched_setaffinity issue above. I haven't yet investigated them, but it may be of interest to review whether any of the actions performed by hotplug states between CPUHP_AP_ONLINE_IDLE & CPUHP_AP_ACTIVE could have similar unintended effects on user tasks that might schedule before they are reached, which might widen the scope of the problem from just affecting the behaviour of sched_setaffinity. Signed-off-by: Paul Burton Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20180526154648.11635-2-paul.burton@mips.com Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

sched/core: Fix rules for running on online && !active CPUs

2018-07-08T13:30:53Z

[ Upstream commit 175f0e25abeaa2218d431141ce19cf1de70fa82d ] As already enforced by the WARN() in __set_cpus_allowed_ptr(), the rules for running on an online && !active CPU are stricter than just being a kthread, you need to be a per-cpu kthread. If you're not strictly per-CPU, you have better CPUs to run on and don't need the partially booted one to get your work done. The exception is to allow smpboot threads to bootstrap the CPU itself and get kernel 'services' initialized before we allow userspace on it. Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Tejun Heo Cc: Thomas Gleixner Fixes: 955dbdf4ce87 ("sched: Allow migrating kthreads into online but inactive CPUs") Link: http://lkml.kernel.org/r/20170725165821.cejhb7v2s3kecems@hirez.programming.kicks-ass.net Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

sched/deadline: Make the grub_reclaim() function static

2018-06-20T19:03:01Z

[ Upstream commit 3febfc8a219a036633b57a34c6678e21b6a0580d ] Since the grub_reclaim() function can be made static, make it so. Silences the following GCC warning (W=1): kernel/sched/deadline.c:1120:5: warning: no previous prototype for ‘grub_reclaim’ [-Wmissing-prototypes] Signed-off-by: Mathieu Malaterre Acked-by: Peter Zijlstra Cc: Linus Torvalds Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20180516200902.959-1-malat@debian.org Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

sched/debug: Move the print_rt_rq() and print_dl_rq() declarations to kernel/sched/sched.h

2018-06-20T19:03:01Z

[ Upstream commit f6a3463063f42d9fb2c78f386437a822e0ad1792 ] In the following commit: 6b55c9654fcc ("sched/debug: Move print_cfs_rq() declaration to kernel/sched/sched.h") the print_cfs_rq() prototype was added to , right next to the prototypes for print_cfs_stats(), print_rt_stats() and print_dl_stats(). Finish this previous commit and also move related prototypes for print_rt_rq() and print_dl_rq(). Remove existing extern declarations now that they not needed anymore. Silences the following GCC warning, triggered by W=1: kernel/sched/debug.c:573:6: warning: no previous prototype for ‘print_rt_rq’ [-Wmissing-prototypes] kernel/sched/debug.c:603:6: warning: no previous prototype for ‘print_dl_rq’ [-Wmissing-prototypes] Signed-off-by: Mathieu Malaterre Acked-by: Peter Zijlstra Cc: Linus Torvalds Cc: Srikar Dronamraju Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20180516195348.30426-1-malat@debian.org Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

sched/core: Introduce set_special_state()

2018-06-20T19:02:54Z

[ Upstream commit b5bf9a90bbebffba888c9144c5a8a10317b04064 ] Gaurav reported a perceived problem with TASK_PARKED, which turned out to be a broken wait-loop pattern in __kthread_parkme(), but the reported issue can (and does) in fact happen for states that do not do condition based sleeps. When the 'current->state = TASK_RUNNING' store of a previous (concurrent) try_to_wake_up() collides with the setting of a 'special' sleep state, we can loose the sleep state. Normal condition based wait-loops are immune to this problem, but for sleep states that are not condition based are subject to this problem. There already is a fix for TASK_DEAD. Abstract that and also apply it to TASK_STOPPED and TASK_TRACED, both of which are also without condition based wait-loop. Reported-by: Gaurav Kohli Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Oleg Nesterov Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman