linux-stable.git/kernel/sched, branch linux-6.11.y

sched/cpufreq: Ensure sd is rebuilt for EAS check

2024-12-05T12:52:52+00:00

[ Upstream commit 70d8b6485b0bcd135b6699fc4252d2272818d1fb ]

Ensure sugov_eas_rebuild_sd() is always called when sugov_init()
succeeds. The out goto initialized sugov without forcing the rebuild.

Previously the missing call to sugov_eas_rebuild_sd() could lead to EAS
not being enabled on boot when it should have been, because it requires
all policies to be controlled by schedutil while they might not have
been initialized yet.

Fixes: e7a1b32e43b1 ("cpufreq: Rebuild sched-domains when removing cpufreq driver")
Signed-off-by: Christian Loehle 
Link: https://patch.msgid.link/35e572d9-1152-406a-9e34-2525f7548af9@arm.com
Signed-off-by: Rafael J. Wysocki 
Signed-off-by: Sasha Levin

sched/numa: Fix the potential null pointer dereference in task_numa_work()

2024-11-08T15:30:57+00:00

[ Upstream commit 9c70b2a33cd2aa6a5a59c5523ef053bd42265209 ]

When running stress-ng-vm-segv test, we found a null pointer dereference
error in task_numa_work(). Here is the backtrace:

  [323676.066985] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000020
  ......
  [323676.067108] CPU: 35 PID: 2694524 Comm: stress-ng-vm-se
  ......
  [323676.067113] pstate: 23401009 (nzCv daif +PAN -UAO +TCO +DIT +SSBS BTYPE=--)
  [323676.067115] pc : vma_migratable+0x1c/0xd0
  [323676.067122] lr : task_numa_work+0x1ec/0x4e0
  [323676.067127] sp : ffff8000ada73d20
  [323676.067128] x29: ffff8000ada73d20 x28: 0000000000000000 x27: 000000003e89f010
  [323676.067130] x26: 0000000000080000 x25: ffff800081b5c0d8 x24: ffff800081b27000
  [323676.067133] x23: 0000000000010000 x22: 0000000104d18cc0 x21: ffff0009f7158000
  [323676.067135] x20: 0000000000000000 x19: 0000000000000000 x18: ffff8000ada73db8
  [323676.067138] x17: 0001400000000000 x16: ffff800080df40b0 x15: 0000000000000035
  [323676.067140] x14: ffff8000ada73cc8 x13: 1fffe0017cc72001 x12: ffff8000ada73cc8
  [323676.067142] x11: ffff80008001160c x10: ffff000be639000c x9 : ffff8000800f4ba4
  [323676.067145] x8 : ffff000810375000 x7 : ffff8000ada73974 x6 : 0000000000000001
  [323676.067147] x5 : 0068000b33e26707 x4 : 0000000000000001 x3 : ffff0009f7158000
  [323676.067149] x2 : 0000000000000041 x1 : 0000000000004400 x0 : 0000000000000000
  [323676.067152] Call trace:
  [323676.067153]  vma_migratable+0x1c/0xd0
  [323676.067155]  task_numa_work+0x1ec/0x4e0
  [323676.067157]  task_work_run+0x78/0xd8
  [323676.067161]  do_notify_resume+0x1ec/0x290
  [323676.067163]  el0_svc+0x150/0x160
  [323676.067167]  el0t_64_sync_handler+0xf8/0x128
  [323676.067170]  el0t_64_sync+0x17c/0x180
  [323676.067173] Code: d2888001 910003fd f9000bf3 aa0003f3 (f9401000)
  [323676.067177] SMP: stopping secondary CPUs
  [323676.070184] Starting crashdump kernel...

stress-ng-vm-segv in stress-ng is used to stress test the SIGSEGV error
handling function of the system, which tries to cause a SIGSEGV error on
return from unmapping the whole address space of the child process.

Normally this program will not cause kernel crashes. But before the
munmap system call returns to user mode, a potential task_numa_work()
for numa balancing could be added and executed. In this scenario, since the
child process has no vma after munmap, the vma_next() in task_numa_work()
will return a null pointer even if the vma iterator restarts from 0.

Recheck the vma pointer before dereferencing it in task_numa_work().

Fixes: 214dbc428137 ("sched: convert to vma iterator")
Signed-off-by: Shawn Wang 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: stable@vger.kernel.org # v6.2+
Link: https://lkml.kernel.org/r/20241025022208.125527-1-shawnwang@linux.alibaba.com
Signed-off-by: Sasha Levin

sched/core: Disable page allocation in task_tick_mm_cid()

2024-11-01T01:02:25+00:00

[ Upstream commit 73ab05aa46b02d96509cb029a8d04fca7bbde8c7 ]

With KASAN and PREEMPT_RT enabled, calling task_work_add() in
task_tick_mm_cid() may cause the following splat.

[   63.696416] BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
[   63.696416] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 610, name: modprobe
[   63.696416] preempt_count: 10001, expected: 0
[   63.696416] RCU nest depth: 1, expected: 1

This problem is caused by the following call trace.

  sched_tick() [ acquire rq->__lock ]
   -> task_tick_mm_cid()
    -> task_work_add()
     -> __kasan_record_aux_stack()
      -> kasan_save_stack()
       -> stack_depot_save_flags()
        -> alloc_pages_mpol_noprof()
         -> __alloc_pages_noprof()
	  -> get_page_from_freelist()
	   -> rmqueue()
	    -> rmqueue_pcplist()
	     -> __rmqueue_pcplist()
	      -> rmqueue_bulk()
	       -> rt_spin_lock()

The rq lock is a raw_spinlock_t. We can't sleep while holding
it. IOW, we can't call alloc_pages() in stack_depot_save_flags().

The task_tick_mm_cid() function with its task_work_add() call was
introduced by commit 223baf9d17f2 ("sched: Fix performance regression
introduced by mm_cid") in v6.4 kernel.

Fortunately, there is a kasan_record_aux_stack_noalloc() variant that
calls stack_depot_save_flags() while not allowing it to allocate
new pages.  To allow task_tick_mm_cid() to use task_work without
page allocation, a new TWAF_NO_ALLOC flag is added to enable calling
kasan_record_aux_stack_noalloc() instead of kasan_record_aux_stack()
if set. The task_tick_mm_cid() function is modified to add this new flag.

The possible downside is the missing stack trace in a KASAN report due
to new page allocation required when task_work_add_noallloc() is called
which should be rare.

Fixes: 223baf9d17f2 ("sched: Fix performance regression introduced by mm_cid")
Signed-off-by: Waiman Long 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20241010014432.194742-1-longman@redhat.com
Signed-off-by: Sasha Levin

sched: psi: fix bogus pressure spikes from aggregation race

2024-10-10T10:03:58+00:00

commit 3840cbe24cf060ea05a585ca497814609f5d47d1 upstream.

Brandon reports sporadic, non-sensical spikes in cumulative pressure
time (total=) when reading cpu.pressure at a high rate. This is due to
a race condition between reader aggregation and tasks changing states.

While it affects all states and all resources captured by PSI, in
practice it most likely triggers with CPU pressure, since scheduling
events are so frequent compared to other resource events.

The race context is the live snooping of ongoing stalls during a
pressure read. The read aggregates per-cpu records for stalls that
have concluded, but will also incorporate ad-hoc the duration of any
active state that hasn't been recorded yet. This is important to get
timely measurements of ongoing stalls. Those ad-hoc samples are
calculated on-the-fly up to the current time on that CPU; since the
stall hasn't concluded, it's expected that this is the minimum amount
of stall time that will enter the per-cpu records once it does.

The problem is that the path that concludes the state uses a CPU clock
read that is not synchronized against aggregators; the clock is read
outside of the seqlock protection. This allows aggregators to race and
snoop a stall with a longer duration than will actually be recorded.

With the recorded stall time being less than the last snapshot
remembered by the aggregator, a subsequent sample will underflow and
observe a bogus delta value, resulting in an erratic jump in pressure.

Fix this by moving the clock read of the state change into the seqlock
protection. This ensures no aggregation can snoop live stalls past the
time that's recorded when the state concludes.

Reported-by: Brandon Duffany 
Link: https://bugzilla.kernel.org/show_bug.cgi?id=219194
Link: https://lore.kernel.org/lkml/20240827121851.GB438928@cmpxchg.org/
Fixes: df77430639c9 ("psi: Reduce calls to sched_clock() in psi")
Cc: stable@vger.kernel.org
Signed-off-by: Johannes Weiner 
Reviewed-by: Chengming Zhou 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

sched/core: Clear prev->dl_server in CFS pick fast path

2024-10-10T10:03:57+00:00

commit a741b82423f41501e301eb6f9820b45ca202e877 upstream.

In case the previous pick was a DL server pick, ->dl_server might be
set. Clear it in the fast path as well.

Fixes: 63ba8422f876 ("sched/deadline: Introduce deadline servers")
Signed-off-by: Youssef Esmat 
Signed-off-by: Daniel Bristot de Oliveira 
Signed-off-by: Peter Zijlstra (Intel) 
Tested-by: Juri Lelli 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/7f7381ccba09efcb4a1c1ff808ed58385eccc222.1716811044.git.bristot@kernel.org
Signed-off-by: Greg Kroah-Hartman

sched/core: Add clearing of ->dl_server in put_prev_task_balance()

2024-10-10T10:03:57+00:00

commit c245910049d04fbfa85bb2f5acd591c24e9907c7 upstream.

Paths using put_prev_task_balance() need to do a pick shortly
after. Make sure they also clear the ->dl_server on prev as a
part of that.

Fixes: 63ba8422f876 ("sched/deadline: Introduce deadline servers")
Signed-off-by: "Joel Fernandes (Google)" 
Signed-off-by: Daniel Bristot de Oliveira 
Signed-off-by: Peter Zijlstra (Intel) 
Tested-by: Juri Lelli 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/d184d554434bedbad0581cb34656582d78655150.1716811044.git.bristot@kernel.org
Signed-off-by: Greg Kroah-Hartman

sched/pelt: Use rq_clock_task() for hw_pressure

2024-10-04T14:38:01+00:00

[ Upstream commit 84d265281d6cea65353fc24146280e0d86ac50cb ]

commit 97450eb90965 ("sched/pelt: Remove shift of thermal clock")
removed the decay_shift for hw_pressure. This commit uses the
sched_clock_task() in sched_tick() while it replaces the
sched_clock_task() with rq_clock_pelt() in __update_blocked_others().
This could bring inconsistence. One possible scenario I can think of
is in ___update_load_sum():

  u64 delta = now - sa->last_update_time

'now' could be calculated by rq_clock_pelt() from
__update_blocked_others(), and last_update_time was calculated by
rq_clock_task() previously from sched_tick(). Usually the former
chases after the latter, it cause a very large 'delta' and brings
unexpected behavior.

Fixes: 97450eb90965 ("sched/pelt: Remove shift of thermal clock")
Signed-off-by: Chen Yu 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Hongyan Xia 
Reviewed-by: Vincent Guittot 
Link: https://lkml.kernel.org/r/20240827112607.181206-1-yu.c.chen@intel.com
Signed-off-by: Sasha Levin

sched/numa: Fix the vma scan starving issue

2024-10-04T14:38:00+00:00

[ Upstream commit f22cde4371f3c624e947a35b075c06c771442a43 ]

Problem statement:
Since commit fc137c0ddab2 ("sched/numa: enhance vma scanning logic"), the
Numa vma scan overhead has been reduced a lot.  Meanwhile, the reducing of
the vma scan might create less Numa page fault information.  The
insufficient information makes it harder for the Numa balancer to make
decision.  Later, commit b7a5b537c55c08 ("sched/numa: Complete scanning of
partial VMAs regardless of PID activity") and commit 84db47ca7146d7
("sched/numa: Fix mm numa_scan_seq based unconditional scan") are found to
bring back part of the performance.

Recently when running SPECcpu omnetpp_r on a 320 CPUs/2 Sockets system, a
long duration of remote Numa node read was observed by PMU events: A few
cores having ~500MB/s remote memory access for ~20 seconds.  It causes
high core-to-core variance and performance penalty.  After the
investigation, it is found that many vmas are skipped due to the active
PID check.  According to the trace events, in most cases,
vma_is_accessed() returns false because the history access info stored in
pids_active array has been cleared.

Proposal:
The main idea is to adjust vma_is_accessed() to let it return true easier.
Thus compare the diff between mm->numa_scan_seq and
vma->numab_state->prev_scan_seq.  If the diff has exceeded the threshold,
scan the vma.

This patch especially helps the cases where there are small number of
threads, like the process-based SPECcpu.  Without this patch, if the
SPECcpu process access the vma at the beginning, then sleeps for a long
time, the pid_active array will be cleared.  A a result, if this process
is woken up again, it never has a chance to set prot_none anymore.
Because only the first 2 times of access is granted for vma scan:
(current->mm->numa_scan_seq) - vma->numab_state->start_scan_seq) < 2 to be
worse, no other threads within the task can help set the prot_none.  This
causes information lost.

Raghavendra helped test current patch and got the positive result
on the AMD platform:

autonumabench NUMA01
                            base                  patched
Amean     syst-NUMA01      194.05 (   0.00%)      165.11 *  14.92%*
Amean     elsp-NUMA01      324.86 (   0.00%)      315.58 *   2.86%*

Duration User      380345.36   368252.04
Duration System      1358.89     1156.23
Duration Elapsed     2277.45     2213.25

autonumabench NUMA02

Amean     syst-NUMA02        1.12 (   0.00%)        1.09 *   2.93%*
Amean     elsp-NUMA02        3.50 (   0.00%)        3.56 *  -1.84%*

Duration User        1513.23     1575.48
Duration System         8.33        8.13
Duration Elapsed       28.59       29.71

kernbench

Amean     user-256    22935.42 (   0.00%)    22535.19 *   1.75%*
Amean     syst-256     7284.16 (   0.00%)     7608.72 *  -4.46%*
Amean     elsp-256      159.01 (   0.00%)      158.17 *   0.53%*

Duration User       68816.41    67615.74
Duration System     21873.94    22848.08
Duration Elapsed      506.66      504.55

Intel 256 CPUs/2 Sockets:
autonuma benchmark also shows improvements:

                                               v6.10-rc5              v6.10-rc5
                                                                         +patch
Amean     syst-NUMA01                  245.85 (   0.00%)      230.84 *   6.11%*
Amean     syst-NUMA01_THREADLOCAL      205.27 (   0.00%)      191.86 *   6.53%*
Amean     syst-NUMA02                   18.57 (   0.00%)       18.09 *   2.58%*
Amean     syst-NUMA02_SMT                2.63 (   0.00%)        2.54 *   3.47%*
Amean     elsp-NUMA01                  517.17 (   0.00%)      526.34 *  -1.77%*
Amean     elsp-NUMA01_THREADLOCAL       99.92 (   0.00%)      100.59 *  -0.67%*
Amean     elsp-NUMA02                   15.81 (   0.00%)       15.72 *   0.59%*
Amean     elsp-NUMA02_SMT               13.23 (   0.00%)       12.89 *   2.53%*

                   v6.10-rc5   v6.10-rc5
                                  +patch
Duration User     1064010.16  1075416.23
Duration System      3307.64     3104.66
Duration Elapsed     4537.54     4604.73

The SPECcpu remote node access issue disappears with the patch applied.

Link: https://lkml.kernel.org/r/20240827112958.181388-1-yu.c.chen@intel.com
Fixes: fc137c0ddab2 ("sched/numa: enhance vma scanning logic")
Signed-off-by: Chen Yu 
Co-developed-by: Chen Yu 
Signed-off-by: Yujie Liu 
Reported-by: Xiaoping Zhou 
Reviewed-and-tested-by: Raghavendra K T 
Acked-by: Mel Gorman 
Cc: "Chen, Tim C" 
Cc: Ingo Molnar 
Cc: Juri Lelli 
Cc: Peter Zijlstra 
Cc: Raghavendra K T 
Cc: Vincent Guittot 
Signed-off-by: Andrew Morton 
Signed-off-by: Sasha Levin

sched/deadline: Fix schedstats vs deadline servers

2024-10-04T14:37:59+00:00

[ Upstream commit 9c602adb799e72ee537c0c7ca7e828c3fe2acad6 ]

In dl_server_start(), when schedstats is enabled, the following
happens:

  dl_server_start()
    dl_se->dl_server = 1;
    enqueue_dl_entity()
      update_stats_enqueue_dl()
        __schedstats_from_dl_se()
          dl_task_of()
            BUG_ON(dl_server(dl_se));

Since only tasks have schedstats and internal entries do not, avoid
trying to update stats in this case.

Fixes: 63ba8422f876 ("sched/deadline: Introduce deadline servers")
Signed-off-by: Huang Shijie 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Juri Lelli 
Link: https://lkml.kernel.org/r/20240829031111.12142-1-shijie@os.amperecomputing.com
Signed-off-by: Sasha Levin

sched/fair: Make SCHED_IDLE entity be preempted in strict hierarchy

2024-10-04T14:37:51+00:00

[ Upstream commit faa42d29419def58d3c3e5b14ad4037f0af3b496 ]

Consider the following cgroup:

                       root
                        |
             ------------------------
             |                      |
       normal_cgroup            idle_cgroup
             |                      |
   SCHED_IDLE task_A           SCHED_NORMAL task_B

According to the cgroup hierarchy, A should preempt B. But current
check_preempt_wakeup_fair() treats cgroup se and task separately, so B
will preempt A unexpectedly.
Unify the wakeup logic by {c,p}se_is_idle only. This makes SCHED_IDLE of
a task a relative policy that is effective only within its own cgroup,
similar to the behavior of NICE.

Also fix se_is_idle() definition when !CONFIG_FAIR_GROUP_SCHED.

Fixes: 304000390f88 ("sched: Cgroup SCHED_IDLE support")
Signed-off-by: Tianchen Ding 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Josh Don 
Reviewed-by: Vincent Guittot 
Link: https://lkml.kernel.org/r/20240626023505.1332596-1-dtcccc@linux.alibaba.com
Signed-off-by: Sasha Levin