From f740e6cd0cb5e7468e46831aeb4d9c30e03d5ebc Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 23 Jun 2011 11:19:28 -0700 Subject: stop_machine: implement stop_machine_from_inactive_cpu() Currently, mtrr wants stop_machine functionality while a CPU is being brought up. As stop_machine() requires the calling CPU to be active, mtrr implements its own stop_machine using stop_one_cpu() on each online CPU. This doesn't only unnecessarily duplicate complex logic but also introduces a possibility of deadlock when it races against the generic stop_machine(). This patch implements stop_machine_from_inactive_cpu() to serve such use cases. Its functionality is basically the same as stop_machine(); however, it should be called from a CPU which isn't active and doesn't depend on working scheduling on the calling CPU. This is achieved by using busy loops for synchronization and open-coding stop_cpus queuing and waiting with direct invocation of fn() for local CPU inbetween. Signed-off-by: Tejun Heo Link: http://lkml.kernel.org/r/20110623182056.982526827@sbsiddha-MOBL3.sc.intel.com Signed-off-by: Suresh Siddha Cc: Ingo Molnar Cc: Andrew Morton Cc: Linus Torvalds Cc: Peter Zijlstra Signed-off-by: H. Peter Anvin --- include/linux/stop_machine.h | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) (limited to 'include/linux/stop_machine.h') diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h index 14d3524d1274..e0f2da25d751 100644 --- a/include/linux/stop_machine.h +++ b/include/linux/stop_machine.h @@ -126,15 +126,19 @@ int stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus); */ int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus); +int stop_machine_from_inactive_cpu(int (*fn)(void *), void *data, + const struct cpumask *cpus); + #else /* CONFIG_STOP_MACHINE && CONFIG_SMP */ static inline int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus) { + unsigned long flags; int ret; - local_irq_disable(); + local_irq_save(flags); ret = fn(data); - local_irq_enable(); + local_irq_restore(flags); return ret; } @@ -144,5 +148,11 @@ static inline int stop_machine(int (*fn)(void *), void *data, return __stop_machine(fn, data, cpus); } +static inline int stop_machine_from_inactive_cpu(int (*fn)(void *), void *data, + const struct cpumask *cpus) +{ + return __stop_machine(fn, data, cpus); +} + #endif /* CONFIG_STOP_MACHINE && CONFIG_SMP */ #endif /* _LINUX_STOP_MACHINE */ -- cgit v1.2.2