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| author | Michal Hocko <mhocko@suse.com> | 2016-12-07 14:54:38 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2016-12-08 10:08:41 +0100 |
| commit | 777c6e0daebb3fcefbbd6f620410a946b07ef6d0 (patch) | |
| tree | c375281eed00226aa72500679f8e3604fe970182 /kernel/cpu.c | |
| parent | 3e5de27e940d00d8d504dfb96625fb654f641509 (diff) | |
| download | linux-777c6e0daebb3fcefbbd6f620410a946b07ef6d0.tar.gz linux-777c6e0daebb3fcefbbd6f620410a946b07ef6d0.tar.bz2 linux-777c6e0daebb3fcefbbd6f620410a946b07ef6d0.zip | |
hotplug: Make register and unregister notifier API symmetric
Yu Zhao has noticed that __unregister_cpu_notifier only unregisters its
notifiers when HOTPLUG_CPU=y while the registration might succeed even
when HOTPLUG_CPU=n if MODULE is enabled. This means that e.g. zswap
might keep a stale notifier on the list on the manual clean up during
the pool tear down and thus corrupt the list. Resulting in the following
[ 144.964346] BUG: unable to handle kernel paging request at ffff880658a2be78
[ 144.971337] IP: [<ffffffffa290b00b>] raw_notifier_chain_register+0x1b/0x40
<snipped>
[ 145.122628] Call Trace:
[ 145.125086] [<ffffffffa28e5cf8>] __register_cpu_notifier+0x18/0x20
[ 145.131350] [<ffffffffa2a5dd73>] zswap_pool_create+0x273/0x400
[ 145.137268] [<ffffffffa2a5e0fc>] __zswap_param_set+0x1fc/0x300
[ 145.143188] [<ffffffffa2944c1d>] ? trace_hardirqs_on+0xd/0x10
[ 145.149018] [<ffffffffa2908798>] ? kernel_param_lock+0x28/0x30
[ 145.154940] [<ffffffffa2a3e8cf>] ? __might_fault+0x4f/0xa0
[ 145.160511] [<ffffffffa2a5e237>] zswap_compressor_param_set+0x17/0x20
[ 145.167035] [<ffffffffa2908d3c>] param_attr_store+0x5c/0xb0
[ 145.172694] [<ffffffffa290848d>] module_attr_store+0x1d/0x30
[ 145.178443] [<ffffffffa2b2b41f>] sysfs_kf_write+0x4f/0x70
[ 145.183925] [<ffffffffa2b2a5b9>] kernfs_fop_write+0x149/0x180
[ 145.189761] [<ffffffffa2a99248>] __vfs_write+0x18/0x40
[ 145.194982] [<ffffffffa2a9a412>] vfs_write+0xb2/0x1a0
[ 145.200122] [<ffffffffa2a9a732>] SyS_write+0x52/0xa0
[ 145.205177] [<ffffffffa2ff4d97>] entry_SYSCALL_64_fastpath+0x12/0x17
This can be even triggered manually by changing
/sys/module/zswap/parameters/compressor multiple times.
Fix this issue by making unregister APIs symmetric to the register so
there are no surprises.
Fixes: 47e627bc8c9a ("[PATCH] hotplug: Allow modules to use the cpu hotplug notifiers even if !CONFIG_HOTPLUG_CPU")
Reported-and-tested-by: Yu Zhao <yuzhao@google.com>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: linux-mm@kvack.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Link: http://lkml.kernel.org/r/20161207135438.4310-1-mhocko@kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/cpu.c')
| -rw-r--r-- | kernel/cpu.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c index 29de1a9352c0..217fd2e7f435 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -659,7 +659,6 @@ void __init cpuhp_threads_init(void) kthread_unpark(this_cpu_read(cpuhp_state.thread)); } -#ifdef CONFIG_HOTPLUG_CPU EXPORT_SYMBOL(register_cpu_notifier); EXPORT_SYMBOL(__register_cpu_notifier); void unregister_cpu_notifier(struct notifier_block *nb) @@ -676,6 +675,7 @@ void __unregister_cpu_notifier(struct notifier_block *nb) } EXPORT_SYMBOL(__unregister_cpu_notifier); +#ifdef CONFIG_HOTPLUG_CPU /** * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU * @cpu: a CPU id |