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Chen Yu db6cc3f4ac Revert "sched/numa: add statistics of numa balance task" 
This reverts commit ad6b26b6a0.

This commit introduces per-memcg/task NUMA balance statistics, but
unfortunately it introduced a NULL pointer exception due to the following
race condition: After a swap task candidate was chosen, its mm_struct
pointer was set to NULL due to task exit.  Later, when performing the
actual task swapping, the p->mm caused the problem.

CPU0                                   CPU1
:
...
task_numa_migrate
     task_numa_find_cpu
      task_numa_compare
        # a normal task p is chosen
        env->best_task = p

                                          # p exit:
                                          exit_signals(p);
                                             p->flags |= PF_EXITING
                                          exit_mm
                                             p->mm = NULL;

      migrate_swap_stop
        __migrate_swap_task((arg->src_task, arg->dst_cpu)
         count_memcg_event_mm(p->mm, NUMA_TASK_SWAP)# p->mm is NULL

task_lock() should be held and the PF_EXITING flag needs to be checked to
prevent this from happening.  After discussion, the conclusion was that
adding a lock is not worthwhile for some statistics calculations.  Revert
the change and rely on the tracepoint for this purpose.

Link: https://lkml.kernel.org/r/20250704135620.685752-1-yu.c.chen@intel.com
Link: https://lkml.kernel.org/r/20250708064917.BBD13C4CEED@smtp.kernel.org
Fixes: ad6b26b6a0 ("sched/numa: add statistics of numa balance task")
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Reported-by: Jirka Hladky <jhladky@redhat.com>
Closes: https://lore.kernel.org/all/CAE4VaGBLJxpd=NeRJXpSCuw=REhC5LWJpC29kDy-Zh2ZDyzQZA@mail.gmail.com/
Reported-by: Srikanth Aithal <Srikanth.Aithal@amd.com>
Reported-by: Suneeth D <Suneeth.D@amd.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Hladky <jhladky@redhat.com>
Cc: Libo Chen <libo.chen@oracle.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2025-07-09 21:07:56 -07:00
..
acpi Merge branches 'acpi-processor' and 'acpi-cppc' 2025-05-26 18:37:38 +02:00
asm-generic hyperv-next for v6.16 2025-06-03 08:39:20 -07:00
clocksource
crypto Crypto library fix for v6.16-rc4 2025-06-27 17:32:30 -07:00
cxl
drm drm/sched: Increment job count before swapping tail spsc queue 2025-07-01 16:14:47 -07:00
dt-bindings USB/Thunderbolt changes for 6.16-rc1 2025-06-06 12:45:35 -07:00
hyperv hyperv-next for v6.16 2025-06-03 08:39:20 -07:00
keys
kunit I've recently moved computers (among other things) so I'm sending this from a 2025-05-30 09:15:40 -07:00
kvm KVM: arm64: Resolve vLPI by host IRQ in vgic_v4_unset_forwarding() 2025-05-30 09:11:29 +01:00
linux Revert "sched/numa: add statistics of numa balance task" 2025-07-09 21:07:56 -07:00
math-emu
media
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net Bluetooth: hci_core: Fix use-after-free in vhci_flush() 2025-06-23 10:59:29 -04:00
pcmcia
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rdma Linux 6.15 2025-05-26 15:33:52 -03:00
rv
scsi SCSI misc on 20250529 2025-05-29 22:17:52 -07:00
soc - The 3 patch series "hung_task: extend blocking task stacktrace dump to 2025-05-31 19:12:53 -07:00
sound USB/Thunderbolt changes for 6.16-rc1 2025-06-06 12:45:35 -07:00
target
trace vfs-6.16-rc5.fixes 2025-07-04 09:06:49 -07:00
uapi block-6.16-20250626 2025-06-27 09:02:33 -07:00
ufs
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video fbdev: atyfb: Remove unused PCI vendor ID 2025-05-31 10:24:01 +02:00
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