From fe5595c074005bd94f0c7d1644175941149f6768 Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Wed, 24 May 2017 10:15:16 +0200 Subject: stop_machine: Provide stop_machine_cpuslocked() Some call sites of stop_machine() are within a get_online_cpus() protected region. stop_machine() calls get_online_cpus() as well, which is possible in the current implementation but prevents converting the hotplug locking to a percpu rwsem. Provide stop_machine_cpuslocked() to avoid nested calls to get_online_cpus(). Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Tested-by: Paul E. McKenney Acked-by: Paul E. McKenney Acked-by: Ingo Molnar Cc: Peter Zijlstra Cc: Steven Rostedt Link: http://lkml.kernel.org/r/20170524081547.400700852@linutronix.de --- include/linux/stop_machine.h | 26 +++++++++++++++++++++++--- 1 file changed, 23 insertions(+), 3 deletions(-) (limited to 'include/linux/stop_machine.h') diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h index 3cc9632dcc2a..3d60275e3ba9 100644 --- a/include/linux/stop_machine.h +++ b/include/linux/stop_machine.h @@ -116,15 +116,29 @@ static inline int try_stop_cpus(const struct cpumask *cpumask, * @fn() runs. * * This can be thought of as a very heavy write lock, equivalent to - * grabbing every spinlock in the kernel. */ + * grabbing every spinlock in the kernel. + * + * Protects against CPU hotplug. + */ int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus); +/** + * stop_machine_cpuslocked: freeze the machine on all CPUs and run this function + * @fn: the function to run + * @data: the data ptr for the @fn() + * @cpus: the cpus to run the @fn() on (NULL = any online cpu) + * + * Same as above. Must be called from with in a cpus_read_lock() protected + * region. Avoids nested calls to cpus_read_lock(). + */ +int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus); + int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus); #else /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */ -static inline int stop_machine(cpu_stop_fn_t fn, void *data, - const struct cpumask *cpus) +static inline int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data, + const struct cpumask *cpus) { unsigned long flags; int ret; @@ -134,6 +148,12 @@ static inline int stop_machine(cpu_stop_fn_t fn, void *data, return ret; } +static inline int stop_machine(cpu_stop_fn_t fn, void *data, + const struct cpumask *cpus) +{ + return stop_machine_cpuslocked(fn, data, cpus); +} + static inline int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus) { -- cgit v1.2.3-59-g8ed1b