Pull scheduler fixes from Thomas Gleixner: - two patches addressing the problem that the scheduler allows under certain conditions user space tasks to be scheduled on CPUs which are not yet fully booted which causes a few subtle and hard to debug issue - add a missing runqueue clock update in the deadline scheduler which triggers a warning under certain circumstances - fix a silly typo in the scheduler header file * 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: sched/headers: Fix typo sched/deadline: Fix missing clock update sched/core: Require cpu_active() in select_task_rq(), for user tasks sched/core: Fix rules for running on online && !active CPUs
I cannot spell 'throttling'. Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20180530224940.17839-1-dave@stgolabs.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
A missing clock update is causing the following warning: rq->clock_update_flags < RQCF_ACT_SKIP WARNING: CPU: 10 PID: 0 at kernel/sched/sched.h:963 inactive_task_timer+0x5d6/0x720 Call Trace: <IRQ> __hrtimer_run_queues+0x10f/0x530 hrtimer_interrupt+0xe5/0x240 smp_apic_timer_interrupt+0x79/0x2b0 apic_timer_interrupt+0xf/0x20 </IRQ> do_idle+0x203/0x280 cpu_startup_entry+0x6f/0x80 start_secondary+0x1b0/0x200 secondary_startup_64+0xa5/0xb0 hardirqs last enabled at (793919): [<ffffffffa27c5f6e>] cpuidle_enter_state+0x9e/0x360 hardirqs last disabled at (793920): [<ffffffffa2a0096e>] interrupt_entry+0xce/0xe0 softirqs last enabled at (793922): [<ffffffffa20bef78>] irq_enter+0x68/0x70 softirqs last disabled at (793921): [<ffffffffa20bef5d>] irq_enter+0x4d/0x70 This happens because inactive_task_timer() calls sub_running_bw() (if TASK_DEAD and non_contending) that might trigger a schedutil update, which might access the clock. Clock is however currently updated only later in inactive_task_timer() function. Fix the problem by updating the clock right after task_rq_lock(). Reported-by: kernel test robot <xiaolong.ye@intel.com> Signed-off-by: Juri Lelli <juri.lelli@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Claudio Scordino <claudio@evidence.eu.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Luca Abeni <luca.abeni@santannapisa.it> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20180530160809.9074-1-juri.lelli@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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 <paul.burton@mips.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20180526154648.11635-2-paul.burton@mips.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
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 <mingo@kernel.org>
Pull tracing fixes from Steven Rostedt:
"While writing selftests for a new feature, I triggered two existing
bugs that deal with triggers and instances.
- a generic trigger bug where the triggers are not removed from a
linked list properly when deleting an instance.
- a bug specific to snapshots, where the snapshot is done in the top
level buffer, when it is supposed to snapshot the buffer associated
to the instance the snapshot trigger exists in"
* tag 'trace-v4.17-rc4-3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
tracing: Make the snapshot trigger work with instances
tracing: Fix crash when freeing instances with event triggers
The snapshot trigger currently only affects the main ring buffer, even when
it is used by the instances. This can be confusing as the snapshot trigger
is listed in the instance.
> # cd /sys/kernel/tracing
> # mkdir instances/foo
> # echo snapshot > instances/foo/events/syscalls/sys_enter_fchownat/trigger
> # echo top buffer > trace_marker
> # echo foo buffer > instances/foo/trace_marker
> # touch /tmp/bar
> # chown rostedt /tmp/bar
> # cat instances/foo/snapshot
# tracer: nop
#
#
# * Snapshot is freed *
#
# Snapshot commands:
# echo 0 > snapshot : Clears and frees snapshot buffer
# echo 1 > snapshot : Allocates snapshot buffer, if not already allocated.
# Takes a snapshot of the main buffer.
# echo 2 > snapshot : Clears snapshot buffer (but does not allocate or free)
# (Doesn't have to be '2' works with any number that
# is not a '0' or '1')
> # cat snapshot
# tracer: nop
#
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / delay
# TASK-PID CPU# |||| TIMESTAMP FUNCTION
# | | | |||| | |
bash-1189 [000] .... 111.488323: tracing_mark_write: top buffer
Not only did the snapshot occur in the top level buffer, but the instance
snapshot buffer should have been allocated, and it is still free.
Cc: stable@vger.kernel.org
Fixes: 85f2b08268c01 ("tracing: Add basic event trigger framework")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
If a instance has an event trigger enabled when it is freed, it could cause
an access of free memory. Here's the case that crashes:
# cd /sys/kernel/tracing
# mkdir instances/foo
# echo snapshot > instances/foo/events/initcall/initcall_start/trigger
# rmdir instances/foo
Would produce:
general protection fault: 0000 [#1] PREEMPT SMP PTI
Modules linked in: tun bridge ...
CPU: 5 PID: 6203 Comm: rmdir Tainted: G W 4.17.0-rc4-test+ #933
Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v03.03 07/14/2016
RIP: 0010:clear_event_triggers+0x3b/0x70
RSP: 0018:ffffc90003783de0 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 6b6b6b6b6b6b6b2b RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8800c7130ba0
RBP: ffffc90003783e00 R08: ffff8801131993f8 R09: 0000000100230016
R10: ffffc90003783d80 R11: 0000000000000000 R12: ffff8800c7130ba0
R13: ffff8800c7130bd8 R14: ffff8800cc093768 R15: 00000000ffffff9c
FS: 00007f6f4aa86700(0000) GS:ffff88011eb40000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6f4a5aed60 CR3: 00000000cd552001 CR4: 00000000001606e0
Call Trace:
event_trace_del_tracer+0x2a/0xc5
instance_rmdir+0x15c/0x200
tracefs_syscall_rmdir+0x52/0x90
vfs_rmdir+0xdb/0x160
do_rmdir+0x16d/0x1c0
__x64_sys_rmdir+0x17/0x20
do_syscall_64+0x55/0x1a0
entry_SYSCALL_64_after_hwframe+0x49/0xbe
This was due to the call the clears out the triggers when an instance is
being deleted not removing the trigger from the link list.
Cc: stable@vger.kernel.org
Fixes: 85f2b08268c01 ("tracing: Add basic event trigger framework")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Pull scheduler fixes from Thomas Gleixner: "Three fixes for scheduler and kthread code: - allow calling kthread_park() on an already parked thread - restore the sched_pi_setprio() tracepoint behaviour - clarify the unclear string for the scheduling domain debug output" * 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: sched, tracing: Fix trace_sched_pi_setprio() for deboosting kthread: Allow kthread_park() on a parked kthread sched/topology: Clarify root domain(s) debug string
Merge misc fixes from Andrew Morton: "16 fixes" * emailed patches from Andrew Morton <akpm@linux-foundation.org>: kasan: fix memory hotplug during boot kasan: free allocated shadow memory on MEM_CANCEL_ONLINE checkpatch: fix macro argument precedence test init/main.c: include <linux/mem_encrypt.h> kernel/sys.c: fix potential Spectre v1 issue mm/memory_hotplug: fix leftover use of struct page during hotplug proc: fix smaps and meminfo alignment mm: do not warn on offline nodes unless the specific node is explicitly requested mm, memory_hotplug: make has_unmovable_pages more robust mm/kasan: don't vfree() nonexistent vm_area MAINTAINERS: change hugetlbfs maintainer and update files ipc/shm: fix shmat() nil address after round-down when remapping Revert "ipc/shm: Fix shmat mmap nil-page protection" idr: fix invalid ptr dereference on item delete ocfs2: revert "ocfs2/o2hb: check len for bio_add_page() to avoid getting incorrect bio" mm: fix nr_rotate_swap leak in swapon() error case