[PATCH v2 0/2] Do not change worker's running cpu in cmci_rediscover().

[Tang Chen]

1. cmci_rediscover() is only called by the CPU_POST_DEAD event handler, which
means the corresponding cpu has already dead. As a result, it won't be accessed
in the for_each_online_cpu loop.
So, we could change the if(cpu == dying) statement into a WARN_ON_ONCE().

2. cmci_rediscover() used set_cpus_allowed_ptr() to change the current process's
running cpu, and migrate itself to the dest cpu. But worker processes are not
allowed to be migrated. If current is a worker, the worker will be migrated to
another cpu, but the corresponding  worker_pool is still on the original cpu.

In this case, the following BUG_ON in try_to_wake_up_local() will be triggered:
BUG_ON(rq != this_rq());

This will cause the kernel panic.

This patch removes the set_cpus_allowed_ptr() call, and put the cmci rediscover
jobs onto all the other cpus using system_wq. This could bring some delay for
the jobs.

The following is call trace.

[ 6155.451107] ------------[ cut here ]------------
[ 6155.452019] kernel BUG at kernel/sched/core.c:1654!
......
[ 6155.452019] RIP: 0010:[<ffffffff810add15>]  [<ffffffff810add15>] try_to_wake_up_local+0x115/0x130
......
[ 6155.452019] Call Trace:
[ 6155.452019]  [<ffffffff8166fc14>] __schedule+0x764/0x880
[ 6155.452019]  [<ffffffff81670059>] schedule+0x29/0x70
[ 6155.452019]  [<ffffffff8166de65>] schedule_timeout+0x235/0x2d0
[ 6155.452019]  [<ffffffff810db57d>] ? mark_held_locks+0x8d/0x140
[ 6155.452019]  [<ffffffff810dd463>] ? __lock_release+0x133/0x1a0
[ 6155.452019]  [<ffffffff81671c50>] ? _raw_spin_unlock_irq+0x30/0x50
[ 6155.452019]  [<ffffffff810db8f5>] ? trace_hardirqs_on_caller+0x105/0x190
[ 6155.452019]  [<ffffffff8166fefb>] wait_for_common+0x12b/0x180
[ 6155.452019]  [<ffffffff810b0b30>] ? try_to_wake_up+0x2f0/0x2f0
[ 6155.452019]  [<ffffffff8167002d>] wait_for_completion+0x1d/0x20
[ 6155.452019]  [<ffffffff8110008a>] stop_one_cpu+0x8a/0xc0
[ 6155.452019]  [<ffffffff810abd40>] ? __migrate_task+0x1a0/0x1a0
[ 6155.452019]  [<ffffffff810a6ab8>] ? complete+0x28/0x60
[ 6155.452019]  [<ffffffff810b0fd8>] set_cpus_allowed_ptr+0x128/0x130
[ 6155.452019]  [<ffffffff81036785>] cmci_rediscover+0xf5/0x140
[ 6155.452019]  [<ffffffff816643c0>] mce_cpu_callback+0x18d/0x19d
[ 6155.452019]  [<ffffffff81676187>] notifier_call_chain+0x67/0x150
[ 6155.452019]  [<ffffffff810a03de>] __raw_notifier_call_chain+0xe/0x10
[ 6155.452019]  [<ffffffff81070470>] __cpu_notify+0x20/0x40
[ 6155.452019]  [<ffffffff810704a5>] cpu_notify_nofail+0x15/0x30
[ 6155.452019]  [<ffffffff81655182>] _cpu_down+0x262/0x2e0
[ 6155.452019]  [<ffffffff81655236>] cpu_down+0x36/0x50
[ 6155.452019]  [<ffffffff813d3eaa>] acpi_processor_remove+0x50/0x11e
[ 6155.452019]  [<ffffffff813a6978>] acpi_device_remove+0x90/0xb2
[ 6155.452019]  [<ffffffff8143cbec>] __device_release_driver+0x7c/0xf0
[ 6155.452019]  [<ffffffff8143cd6f>] device_release_driver+0x2f/0x50
[ 6155.452019]  [<ffffffff813a7870>] acpi_bus_remove+0x32/0x6d
[ 6155.452019]  [<ffffffff813a7932>] acpi_bus_trim+0x87/0xee
[ 6155.452019]  [<ffffffff813a7a21>] acpi_bus_hot_remove_device+0x88/0x16b
[ 6155.452019]  [<ffffffff813a33ee>] acpi_os_execute_deferred+0x27/0x34
[ 6155.452019]  [<ffffffff81090589>] process_one_work+0x219/0x680
[ 6155.452019]  [<ffffffff81090528>] ? process_one_work+0x1b8/0x680
[ 6155.452019]  [<ffffffff813a33c7>] ? acpi_os_wait_events_complete+0x23/0x23
[ 6155.452019]  [<ffffffff810923be>] worker_thread+0x12e/0x320
[ 6155.452019]  [<ffffffff81092290>] ? manage_workers+0x110/0x110
[ 6155.452019]  [<ffffffff81098396>] kthread+0xc6/0xd0
[ 6155.452019]  [<ffffffff8167c4c4>] kernel_thread_helper+0x4/0x10
[ 6155.452019]  [<ffffffff81671f30>] ? retint_restore_args+0x13/0x13
[ 6155.452019]  [<ffffffff810982d0>] ? __init_kthread_worker+0x70/0x70
[ 6155.452019]  [<ffffffff8167c4c0>] ? gs_change+0x13/0x13


Tang Chen (2):
  Replace if statement with WARN_ON_ONCE() in cmci_rediscover().
  Do not change worker's running cpu in cmci_rediscover().

 arch/x86/kernel/cpu/mcheck/mce_intel.c |   34 +++++++++++++++++--------------
 1 files changed, 19 insertions(+), 15 deletions(-)

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