On 02/10/2014 04:21 PM, Gautham R Shenoy wrote: > On Mon, Feb 10, 2014 at 02:45:55PM +0530, Srivatsa S. Bhat wrote: >> Hi Gautham, >> >> On 02/08/2014 12:41 AM, Gautham R Shenoy wrote: >>> On Thu, Feb 06, 2014 at 07:41:03PM +0100, Oleg Nesterov wrote: >>>> On 02/06, Srivatsa S. Bhat wrote: >>>>> >>>>> The following method of CPU hotplug callback registration is not safe >>>>> due to the possibility of an ABBA deadlock involving the >>>>> cpu_add_remove_lock >>>>> and the cpu_hotplug.lock. >>>> [...] >> This patch looks good to me. I have a couple of suggestions though.. >> > > Thanks. I have incorporated the suggestions. Could you check if the > following looks good ? > > --- > Add lockdep annotations for get/put_online_cpus() and > cpu_hotplug_begin()/cpu_hotplug_end(). > > Cc: Oleg Nesterov <[email protected]> > Cc: Srivatsa Bhat <[email protected]> > Signed-off-by: Gautham R. Shenoy <[email protected]>
Reviewed-by: Srivatsa S. Bhat <[email protected]> Regards, Srivatsa S. Bhat > --- > kernel/cpu.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/kernel/cpu.c b/kernel/cpu.c > index deff2e6..33caf5e 100644 > --- a/kernel/cpu.c > +++ b/kernel/cpu.c > @@ -19,6 +19,7 @@ > #include <linux/mutex.h> > #include <linux/gfp.h> > #include <linux/suspend.h> > +#include <linux/lockdep.h> > > #include "smpboot.h" > > @@ -57,17 +58,30 @@ static struct { > * an ongoing cpu hotplug operation. > */ > int refcount; > + > +#ifdef CONFIG_DEBUG_LOCK_ALLOC > + struct lockdep_map dep_map; > +#endif > } cpu_hotplug = { > .active_writer = NULL, > .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock), > .refcount = 0, > +#ifdef CONFIG_DEBUG_LOCK_ALLOC > + .dep_map = {.name = "cpu_hotplug.lock" }, > +#endif > }; > > +/* Lockdep annotations for get/put_online_cpus() and cpu_hotplug_begin/end() > */ > +#define cpuhp_lock_acquire_read() lock_map_acquire_read(&cpu_hotplug.dep_map) > +#define cpuhp_lock_acquire() lock_map_acquire(&cpu_hotplug.dep_map) > +#define cpuhp_lock_release() lock_map_release(&cpu_hotplug.dep_map) > + > void get_online_cpus(void) > { > might_sleep(); > if (cpu_hotplug.active_writer == current) > return; > + cpuhp_lock_acquire_read(); > mutex_lock(&cpu_hotplug.lock); > cpu_hotplug.refcount++; > mutex_unlock(&cpu_hotplug.lock); > @@ -87,6 +101,7 @@ void put_online_cpus(void) > if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer)) > wake_up_process(cpu_hotplug.active_writer); > mutex_unlock(&cpu_hotplug.lock); > + cpuhp_lock_release(); > > } > EXPORT_SYMBOL_GPL(put_online_cpus); > @@ -117,6 +132,7 @@ void cpu_hotplug_begin(void) > { > cpu_hotplug.active_writer = current; > > + cpuhp_lock_acquire(); > for (;;) { > mutex_lock(&cpu_hotplug.lock); > if (likely(!cpu_hotplug.refcount)) > @@ -131,6 +147,7 @@ void cpu_hotplug_done(void) > { > cpu_hotplug.active_writer = NULL; > mutex_unlock(&cpu_hotplug.lock); > + cpuhp_lock_release(); > } > > /* > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
