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| author | Waiman Long <longman@redhat.com> | 2018-07-24 14:26:04 -0400 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2018-07-26 10:37:36 +0200 |
| commit | 6f4ceee9305dc3fe74099159b460f4b56b506f1d (patch) | |
| tree | 167a0733c55bae01d2ccb6ac7c0148144d0b3589 | |
| parent | 601b218568a107370086dc5c7a1b283f8d463268 (diff) | |
| download | linux-6f4ceee9305dc3fe74099159b460f4b56b506f1d.tar.bz2 | |
cpu/hotplug: Add a cpus_read_trylock() function
There are use cases where it can be useful to have a cpus_read_trylock()
function to work around circular lock dependency problem involving
the cpu_hotplug_lock.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
| -rw-r--r-- | include/linux/cpu.h | 2 | ||||
| -rw-r--r-- | kernel/cpu.c | 6 |
2 files changed, 8 insertions, 0 deletions
diff --git a/include/linux/cpu.h b/include/linux/cpu.h index a97a63eef59f..e850bfea3e84 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -103,6 +103,7 @@ extern void cpus_write_lock(void); extern void cpus_write_unlock(void); extern void cpus_read_lock(void); extern void cpus_read_unlock(void); +extern int cpus_read_trylock(void); extern void lockdep_assert_cpus_held(void); extern void cpu_hotplug_disable(void); extern void cpu_hotplug_enable(void); @@ -115,6 +116,7 @@ static inline void cpus_write_lock(void) { } static inline void cpus_write_unlock(void) { } static inline void cpus_read_lock(void) { } static inline void cpus_read_unlock(void) { } +static inline int cpus_read_trylock(void) { return true; } static inline void lockdep_assert_cpus_held(void) { } static inline void cpu_hotplug_disable(void) { } static inline void cpu_hotplug_enable(void) { } diff --git a/kernel/cpu.c b/kernel/cpu.c index 0db8938fbb23..307486baa477 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -290,6 +290,12 @@ void cpus_read_lock(void) } EXPORT_SYMBOL_GPL(cpus_read_lock); +int cpus_read_trylock(void) +{ + return percpu_down_read_trylock(&cpu_hotplug_lock); +} +EXPORT_SYMBOL_GPL(cpus_read_trylock); + void cpus_read_unlock(void) { percpu_up_read(&cpu_hotplug_lock); |