linux-stable.git/kernel/sched, branch v5.10.142

sched/fair: Fix fault in reweight_entity

2022-08-21T13:16:26+00:00

commit 13765de8148f71fa795e0a6607de37c49ea5915a upstream.

Syzbot found a GPF in reweight_entity. This has been bisected to
commit 4ef0c5c6b5ba ("kernel/sched: Fix sched_fork() access an invalid
sched_task_group")

There is a race between sched_post_fork() and setpriority(PRIO_PGRP)
within a thread group that causes a null-ptr-deref in
reweight_entity() in CFS. The scenario is that the main process spawns
number of new threads, which then call setpriority(PRIO_PGRP, 0, -20),
wait, and exit.  For each of the new threads the copy_process() gets
invoked, which adds the new task_struct and calls sched_post_fork()
for it.

In the above scenario there is a possibility that
setpriority(PRIO_PGRP) and set_one_prio() will be called for a thread
in the group that is just being created by copy_process(), and for
which the sched_post_fork() has not been executed yet. This will
trigger a null pointer dereference in reweight_entity(), as it will
try to access the run queue pointer, which hasn't been set.

Before the mentioned change the cfs_rq pointer for the task  has been
set in sched_fork(), which is called much earlier in copy_process(),
before the new task is added to the thread_group.  Now it is done in
the sched_post_fork(), which is called after that.  To fix the issue
the remove the update_load param from the update_load param() function
and call reweight_task() only if the task flag doesn't have the
TASK_NEW flag set.

Fixes: 4ef0c5c6b5ba ("kernel/sched: Fix sched_fork() access an invalid sched_task_group")
Reported-by: syzbot+af7a719bc92395ee41b3@syzkaller.appspotmail.com
Signed-off-by: Tadeusz Struk 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Dietmar Eggemann 
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20220203161846.1160750-1-tadeusz.struk@linaro.org
Signed-off-by: Fedor Pchelkin 
Signed-off-by: Greg Kroah-Hartman

sched: Fix the check of nr_running at queue wakelist

2022-08-21T13:16:13+00:00

[ Upstream commit 28156108fecb1f808b21d216e8ea8f0d205a530c ]

The commit 2ebb17717550 ("sched/core: Offload wakee task activation if it
the wakee is descheduling") checked rq->nr_running <= 1 to avoid task
stacking when WF_ON_CPU.

Per the ordering of writes to p->on_rq and p->on_cpu, observing p->on_cpu
(WF_ON_CPU) in ttwu_queue_cond() implies !p->on_rq, IOW p has gone through
the deactivate_task() in __schedule(), thus p has been accounted out of
rq->nr_running. As such, the task being the only runnable task on the rq
implies reading rq->nr_running == 0 at that point.

The benchmark result is in [1].

[1] https://lore.kernel.org/all/e34de686-4e85-bde1-9f3c-9bbc86b38627@linux.alibaba.com/

Suggested-by: Valentin Schneider 
Signed-off-by: Tianchen Ding 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Valentin Schneider 
Link: https://lore.kernel.org/r/20220608233412.327341-2-dtcccc@linux.alibaba.com
Signed-off-by: Sasha Levin

sched, cpuset: Fix dl_cpu_busy() panic due to empty cs->cpus_allowed

2022-08-21T13:16:12+00:00

[ Upstream commit b6e8d40d43ae4dec00c8fea2593eeea3114b8f44 ]

With cgroup v2, the cpuset's cpus_allowed mask can be empty indicating
that the cpuset will just use the effective CPUs of its parent. So
cpuset_can_attach() can call task_can_attach() with an empty mask.
This can lead to cpumask_any_and() returns nr_cpu_ids causing the call
to dl_bw_of() to crash due to percpu value access of an out of bound
CPU value. For example:

	[80468.182258] BUG: unable to handle page fault for address: ffffffff8b6648b0
	  :
	[80468.191019] RIP: 0010:dl_cpu_busy+0x30/0x2b0
	  :
	[80468.207946] Call Trace:
	[80468.208947]  cpuset_can_attach+0xa0/0x140
	[80468.209953]  cgroup_migrate_execute+0x8c/0x490
	[80468.210931]  cgroup_update_dfl_csses+0x254/0x270
	[80468.211898]  cgroup_subtree_control_write+0x322/0x400
	[80468.212854]  kernfs_fop_write_iter+0x11c/0x1b0
	[80468.213777]  new_sync_write+0x11f/0x1b0
	[80468.214689]  vfs_write+0x1eb/0x280
	[80468.215592]  ksys_write+0x5f/0xe0
	[80468.216463]  do_syscall_64+0x5c/0x80
	[80468.224287]  entry_SYSCALL_64_after_hwframe+0x44/0xae

Fix that by using effective_cpus instead. For cgroup v1, effective_cpus
is the same as cpus_allowed. For v2, effective_cpus is the real cpumask
to be used by tasks within the cpuset anyway.

Also update task_can_attach()'s 2nd argument name to cs_effective_cpus to
reflect the change. In addition, a check is added to task_can_attach()
to guard against the possibility that cpumask_any_and() may return a
value >= nr_cpu_ids.

Fixes: 7f51412a415d ("sched/deadline: Fix bandwidth check/update when migrating tasks between exclusive cpusets")
Signed-off-by: Waiman Long 
Signed-off-by: Ingo Molnar 
Acked-by: Juri Lelli 
Link: https://lore.kernel.org/r/20220803015451.2219567-1-longman@redhat.com
Signed-off-by: Sasha Levin

sched/deadline: Merge dl_task_can_attach() and dl_cpu_busy()

2022-08-21T13:16:12+00:00

[ Upstream commit 772b6539fdda31462cc08368e78df60b31a58bab ]

Both functions are doing almost the same, that is checking if admission
control is still respected.

With exclusive cpusets, dl_task_can_attach() checks if the destination
cpuset (i.e. its root domain) has enough CPU capacity to accommodate the
task.
dl_cpu_busy() checks if there is enough CPU capacity in the cpuset in
case the CPU is hot-plugged out.

dl_task_can_attach() is used to check if a task can be admitted while
dl_cpu_busy() is used to check if a CPU can be hotplugged out.

Make dl_cpu_busy() able to deal with a task and use it instead of
dl_task_can_attach() in task_can_attach().

Signed-off-by: Dietmar Eggemann 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Juri Lelli 
Link: https://lore.kernel.org/r/20220302183433.333029-4-dietmar.eggemann@arm.com
Signed-off-by: Sasha Levin

nohz/full, sched/rt: Fix missed tick-reenabling bug in dequeue_task_rt()

2022-08-21T13:15:36+00:00

[ Upstream commit 5c66d1b9b30f737fcef85a0b75bfe0590e16b62a ]

dequeue_task_rt() only decrements 'rt_rq->rt_nr_running' after having
called sched_update_tick_dependency() preventing it from re-enabling the
tick on systems that no longer have pending SCHED_RT tasks but have
multiple runnable SCHED_OTHER tasks:

  dequeue_task_rt()
    dequeue_rt_entity()
      dequeue_rt_stack()
        dequeue_top_rt_rq()
	  sub_nr_running()	// decrements rq->nr_running
	    sched_update_tick_dependency()
	      sched_can_stop_tick()	// checks rq->rt.rt_nr_running,
	      ...
        __dequeue_rt_entity()
          dec_rt_tasks()	// decrements rq->rt.rt_nr_running
	  ...

Every other scheduler class performs the operation in the opposite
order, and sched_update_tick_dependency() expects the values to be
updated as such. So avoid the misbehaviour by inverting the order in
which the above operations are performed in the RT scheduler.

Fixes: 76d92ac305f2 ("sched: Migrate sched to use new tick dependency mask model")
Signed-off-by: Nicolas Saenz Julienne 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Valentin Schneider 
Reviewed-by: Phil Auld 
Link: https://lore.kernel.org/r/20220628092259.330171-1-nsaenzju@redhat.com
Signed-off-by: Sasha Levin

sched/deadline: Fix BUG_ON condition for deboosted tasks

2022-07-29T15:19:24+00:00

commit ddfc710395cccc61247348df9eb18ea50321cbed upstream.

Tasks the are being deboosted from SCHED_DEADLINE might enter
enqueue_task_dl() one last time and hit an erroneous BUG_ON condition:
since they are not boosted anymore, the if (is_dl_boosted()) branch is
not taken, but the else if (!dl_prio) is and inside this one we
BUG_ON(!is_dl_boosted), which is of course false (BUG_ON triggered)
otherwise we had entered the if branch above. Long story short, the
current condition doesn't make sense and always leads to triggering of a
BUG.

Fix this by only checking enqueue flags, properly: ENQUEUE_REPLENISH has
to be present, but additional flags are not a problem.

Fixes: 64be6f1f5f71 ("sched/deadline: Don't replenish from a !SCHED_DEADLINE entity")
Signed-off-by: Juri Lelli 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20220714151908.533052-1-juri.lelli@redhat.com
Signed-off-by: Greg Kroah-Hartman

sched/fair: Fix cfs_rq_clock_pelt() for throttled cfs_rq

2022-06-09T08:21:02+00:00

[ Upstream commit 64eaf50731ac0a8c76ce2fedd50ef6652aabc5ff ]

Since commit 23127296889f ("sched/fair: Update scale invariance of PELT")
change to use rq_clock_pelt() instead of rq_clock_task(), we should also
use rq_clock_pelt() for throttled_clock_task_time and throttled_clock_task
accounting to get correct cfs_rq_clock_pelt() of throttled cfs_rq. And
rename throttled_clock_task(_time) to be clock_pelt rather than clock_task.

Fixes: 23127296889f ("sched/fair: Update scale invariance of PELT")
Signed-off-by: Chengming Zhou 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Ben Segall 
Reviewed-by: Vincent Guittot 
Link: https://lore.kernel.org/r/20220408115309.81603-1-zhouchengming@bytedance.com
Signed-off-by: Sasha Levin

sched/pelt: Fix attach_entity_load_avg() corner case

2022-04-27T11:53:56+00:00

[ Upstream commit 40f5aa4c5eaebfeaca4566217cb9c468e28ed682 ]

The warning in cfs_rq_is_decayed() triggered:

    SCHED_WARN_ON(cfs_rq->avg.load_avg ||
		  cfs_rq->avg.util_avg ||
		  cfs_rq->avg.runnable_avg)

There exists a corner case in attach_entity_load_avg() which will
cause load_sum to be zero while load_avg will not be.

Consider se_weight is 88761 as per the sched_prio_to_weight[] table.
Further assume the get_pelt_divider() is 47742, this gives:
se->avg.load_avg is 1.

However, calculating load_sum:

  se->avg.load_sum = div_u64(se->avg.load_avg * se->avg.load_sum, se_weight(se));
  se->avg.load_sum = 1*47742/88761 = 0.

Then enqueue_load_avg() adds this to the cfs_rq totals:

  cfs_rq->avg.load_avg += se->avg.load_avg;
  cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum;

Resulting in load_avg being 1 with load_sum is 0, which will trigger
the WARN.

Fixes: f207934fb79d ("sched/fair: Align PELT windows between cfs_rq and its se")
Signed-off-by: kuyo chang 
[peterz: massage changelog]
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Vincent Guittot 
Tested-by: Dietmar Eggemann 
Link: https://lkml.kernel.org/r/20220414090229.342-1-kuyo.chang@mediatek.com
Signed-off-by: Sasha Levin

sched/core: Export pelt_thermal_tp

2022-04-08T12:40:03+00:00

[ Upstream commit 77cf151b7bbdfa3577b3c3f3a5e267a6c60a263b ]

We can't use this tracepoint in modules without having the symbol
exported first, fix that.

Fixes: 765047932f15 ("sched/pelt: Add support to track thermal pressure")
Signed-off-by: Qais Yousef 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20211028115005.873539-1-qais.yousef@arm.com
Signed-off-by: Sasha Levin

sched/debug: Remove mpol_get/put and task_lock/unlock from sched_show_numa

2022-04-08T12:40:03+00:00

[ Upstream commit 28c988c3ec29db74a1dda631b18785958d57df4f ]

The older format of /proc/pid/sched printed home node info which
required the mempolicy and task lock around mpol_get(). However
the format has changed since then and there is no need for
sched_show_numa() any more to have mempolicy argument,
asssociated mpol_get/put and task_lock/unlock. Remove them.

Fixes: 397f2378f1361 ("sched/numa: Fix numa balancing stats in /proc/pid/sched")
Signed-off-by: Bharata B Rao 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Srikar Dronamraju 
Acked-by: Mel Gorman 
Link: https://lore.kernel.org/r/20220118050515.2973-1-bharata@amd.com
Signed-off-by: Sasha Levin