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stop_machine: implement stop_machine_from_inactive_cpu()

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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 <tj@kernel.org>
Link: http://lkml.kernel.org/r/20110623182056.982526827@sbsiddha-MOBL3.sc.intel.com
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
Tejun Heo
2011-06-23 11:19:28 -07:00
committed by H. Peter Anvin
parent fd7355ba1e
commit f740e6cd0c
2 changed files with 73 additions and 3 deletions
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14
include/linux/stop_machine.h
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@@ -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 */