linux/kernel/sched, branch v5.7

sched/fair: Don't NUMA balance for kthreads

2020-05-26T16:34:58Z

Stefano reported a crash with using SQPOLL with io_uring: BUG: kernel NULL pointer dereference, address: 00000000000003b0 CPU: 2 PID: 1307 Comm: io_uring-sq Not tainted 5.7.0-rc7 #11 RIP: 0010:task_numa_work+0x4f/0x2c0 Call Trace: task_work_run+0x68/0xa0 io_sq_thread+0x252/0x3d0 kthread+0xf9/0x130 ret_from_fork+0x35/0x40 which is task_numa_work() oopsing on current->mm being NULL. The task work is queued by task_tick_numa(), which checks if current->mm is NULL at the time of the call. But this state isn't necessarily persistent, if the kthread is using use_mm() to temporarily adopt the mm of a task. Change the task_tick_numa() check to exclude kernel threads in general, as it doesn't make sense to attempt ot balance for kthreads anyway. Reported-by: Stefano Garzarella Signed-off-by: Jens Axboe Signed-off-by: Ingo Molnar Acked-by: Peter Zijlstra Link: https://lore.kernel.org/r/865de121-8190-5d30-ece5-3b097dc74431@kernel.dk

sched/fair: Fix unthrottle_cfs_rq() for leaf_cfs_rq list

2020-05-19T18:34:10Z

Although not exactly identical, unthrottle_cfs_rq() and enqueue_task_fair() are quite close and follow the same sequence for enqueuing an entity in the cfs hierarchy. Modify unthrottle_cfs_rq() to use the same pattern as enqueue_task_fair(). This fixes a problem already faced with the latter and add an optimization in the last for_each_sched_entity loop. Fixes: fe61468b2cb (sched/fair: Fix enqueue_task_fair warning) Reported-by Tao Zhou Signed-off-by: Vincent Guittot Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Phil Auld Reviewed-by: Ben Segall Link: https://lkml.kernel.org/r/20200513135528.4742-1-vincent.guittot@linaro.org

sched/debug: Fix requested task uclamp values shown in procfs

2020-05-19T18:34:10Z

The intention of commit 96e74ebf8d59 ("sched/debug: Add task uclamp values to SCHED_DEBUG procfs") was to print requested and effective task uclamp values. The requested values printed are read from p->uclamp, which holds the last effective values. Fix this by printing the values from p->uclamp_req. Fixes: 96e74ebf8d59 ("sched/debug: Add task uclamp values to SCHED_DEBUG procfs") Signed-off-by: Pavankumar Kondeti Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Valentin Schneider Tested-by: Valentin Schneider Link: https://lkml.kernel.org/r/1589115401-26391-1-git-send-email-pkondeti@codeaurora.org

sched/fair: Fix enqueue_task_fair() warning some more

2020-05-19T18:34:10Z

sched/fair: Fix enqueue_task_fair warning some more The recent patch, fe61468b2cb (sched/fair: Fix enqueue_task_fair warning) did not fully resolve the issues with the rq->tmp_alone_branch != &rq->leaf_cfs_rq_list warning in enqueue_task_fair. There is a case where the first for_each_sched_entity loop exits due to on_rq, having incompletely updated the list. In this case the second for_each_sched_entity loop can further modify se. The later code to fix up the list management fails to do what is needed because se does not point to the sched_entity which broke out of the first loop. The list is not fixed up because the throttled parent was already added back to the list by a task enqueue in a parallel child hierarchy. Address this by calling list_add_leaf_cfs_rq if there are throttled parents while doing the second for_each_sched_entity loop. Fixes: fe61468b2cb ("sched/fair: Fix enqueue_task_fair warning") Suggested-by: Vincent Guittot Signed-off-by: Phil Auld Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Dietmar Eggemann Reviewed-by: Vincent Guittot Link: https://lkml.kernel.org/r/20200512135222.GC2201@lorien.usersys.redhat.com

sched/core: Fix reset-on-fork from RT with uclamp

2020-04-22T21:10:13Z

uclamp_fork() resets the uclamp values to their default when the reset-on-fork flag is set. It also checks whether the task has a RT policy, and sets its uclamp.min to 1024 accordingly. However, during reset-on-fork, the task's policy is lowered to SCHED_NORMAL right after, hence leading to an erroneous uclamp.min setting for the new task if it was forked from RT. Fix this by removing the unnecessary check on rt_task() in uclamp_fork() as this doesn't make sense if the reset-on-fork flag is set. Fixes: 1a00d999971c ("sched/uclamp: Set default clamps for RT tasks") Reported-by: Chitti Babu Theegala Signed-off-by: Quentin Perret Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Patrick Bellasi Reviewed-by: Dietmar Eggemann Link: https://lkml.kernel.org/r/20200416085956.217587-1-qperret@google.com

sched/vtime: Work around an unitialized variable warning

2020-04-15T09:06:50Z

Work around this warning: kernel/sched/cputime.c: In function ‘kcpustat_field’: kernel/sched/cputime.c:1007:6: warning: ‘val’ may be used uninitialized in this function [-Wmaybe-uninitialized] because GCC can't see that val is used only when err is 0. Acked-by: Peter Zijlstra Signed-off-by: Borislav Petkov Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20200327214334.GF8015@zn.tnic

sched/isolation: Allow "isolcpus=" to skip unknown sub-parameters

2020-04-15T08:38:26Z

The "isolcpus=" parameter allows sub-parameters before the cpulist is specified, and if the parser detects an unknown sub-parameters the whole parameter will be ignored. This design is incompatible with itself when new sub-parameters are added. An older kernel will not recognize the new sub-parameter and will invalidate the whole parameter so the CPU isolation will not take effect. It emits a warning: isolcpus: Error, unknown flag The better and compatible way is to allow "isolcpus=" to skip unknown sub-parameters, so that even if new sub-parameters are added an older kernel will still be able to behave as usual even if with the new sub-parameter specified on the command line. Ideally this should have been there when the first sub-parameter for "isolcpus=" was introduced. Suggested-by: Thomas Gleixner Signed-off-by: Peter Xu Signed-off-by: Thomas Gleixner Link: https://lkml.kernel.org/r/20200403223517.406353-1-peterx@redhat.com

sched/debug: Add task uclamp values to SCHED_DEBUG procfs

2020-04-08T09:35:27Z

Requested and effective uclamp values can be a bit tricky to decipher when playing with cgroup hierarchies. Add them to a task's procfs when SCHED_DEBUG is enabled. Reviewed-by: Qais Yousef Signed-off-by: Valentin Schneider Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Link: https://lkml.kernel.org/r/20200226124543.31986-4-valentin.schneider@arm.com

sched/debug: Factor out printing formats into common macros

2020-04-08T09:35:26Z

The printing macros in debug.c keep redefining the same output format. Collect each output format in a single definition, and reuse that definition in the other macros. While at it, add a layer of parentheses and replace printf's with the newly introduced macros. Reviewed-by: Qais Yousef Signed-off-by: Valentin Schneider Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Link: https://lkml.kernel.org/r/20200226124543.31986-3-valentin.schneider@arm.com

sched/debug: Remove redundant macro define

2020-04-08T09:35:24Z

Most printing macros for procfs are defined globally in debug.c, and they are re-defined (to the exact same thing) within proc_sched_show_task(). Get rid of the duplicate defines. Reviewed-by: Qais Yousef Signed-off-by: Valentin Schneider Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Link: https://lkml.kernel.org/r/20200226124543.31986-2-valentin.schneider@arm.com