Commit 6f4ceee9 authored by Waiman Long's avatar Waiman Long Committed by Rafael J. Wysocki

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: default avatarWaiman Long <longman@redhat.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 601b2185
......@@ -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) { }
......
......@@ -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);
......
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