Message ID | 20190531115303.16459-1-jgross@suse.com (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | [v2] xen: remove on-stack cpumask from stop_machine_run() | expand |
>>> On 31.05.19 at 13:53, <jgross@suse.com> wrote: > The "allbutself" cpumask in stop_machine_run() is not needed. Instead > of allocating it on the stack it can easily be avoided. > > Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Jan Beulich <jbeulich@suse.com> with one further remark: > --- a/xen/common/stop_machine.c > +++ b/xen/common/stop_machine.c > @@ -69,8 +69,8 @@ static void stopmachine_wait_state(void) > > int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu) > { > - cpumask_t allbutself; > unsigned int i, nr_cpus; > + unsigned int this = smp_processor_id(); > int ret; > > BUG_ON(!local_irq_is_enabled()); > @@ -79,9 +79,9 @@ int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu) > if ( !get_cpu_maps() ) > return -EBUSY; > > - cpumask_andnot(&allbutself, &cpu_online_map, > - cpumask_of(smp_processor_id())); > - nr_cpus = cpumask_weight(&allbutself); > + nr_cpus = num_online_cpus(); > + if ( cpu_online(this) ) > + nr_cpus--; > > /* Must not spin here as the holder will expect us to be descheduled. */ > if ( !spin_trylock(&stopmachine_lock) ) > @@ -100,8 +100,9 @@ int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu) > > smp_wmb(); > > - for_each_cpu ( i, &allbutself ) > - tasklet_schedule_on_cpu(&per_cpu(stopmachine_tasklet, i), i); > + for_each_online_cpu ( i ) > + if ( i != this ) > + tasklet_schedule_on_cpu(&per_cpu(stopmachine_tasklet, i), i); > > stopmachine_set_state(STOPMACHINE_PREPARE); > stopmachine_wait_state(); A few lines down from here there's another use of smp_processor_id(). If I end up committing this I may take the liberty and also change that to "this", unless you object. Jan
On 31/05/2019 06:06, Jan Beulich wrote: >>>> On 31.05.19 at 13:53, <jgross@suse.com> wrote: >> The "allbutself" cpumask in stop_machine_run() is not needed. Instead >> of allocating it on the stack it can easily be avoided. >> >> Signed-off-by: Juergen Gross <jgross@suse.com> > Reviewed-by: Jan Beulich <jbeulich@suse.com> LGTM. Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
diff --git a/xen/common/stop_machine.c b/xen/common/stop_machine.c index ce6f5624c4..74d04427bd 100644 --- a/xen/common/stop_machine.c +++ b/xen/common/stop_machine.c @@ -69,8 +69,8 @@ static void stopmachine_wait_state(void) int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu) { - cpumask_t allbutself; unsigned int i, nr_cpus; + unsigned int this = smp_processor_id(); int ret; BUG_ON(!local_irq_is_enabled()); @@ -79,9 +79,9 @@ int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu) if ( !get_cpu_maps() ) return -EBUSY; - cpumask_andnot(&allbutself, &cpu_online_map, - cpumask_of(smp_processor_id())); - nr_cpus = cpumask_weight(&allbutself); + nr_cpus = num_online_cpus(); + if ( cpu_online(this) ) + nr_cpus--; /* Must not spin here as the holder will expect us to be descheduled. */ if ( !spin_trylock(&stopmachine_lock) ) @@ -100,8 +100,9 @@ int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu) smp_wmb(); - for_each_cpu ( i, &allbutself ) - tasklet_schedule_on_cpu(&per_cpu(stopmachine_tasklet, i), i); + for_each_online_cpu ( i ) + if ( i != this ) + tasklet_schedule_on_cpu(&per_cpu(stopmachine_tasklet, i), i); stopmachine_set_state(STOPMACHINE_PREPARE); stopmachine_wait_state();
The "allbutself" cpumask in stop_machine_run() is not needed. Instead of allocating it on the stack it can easily be avoided. Signed-off-by: Juergen Gross <jgross@suse.com> --- xen/common/stop_machine.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-)