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smp/up: Make smp_call_function_single() match SMP semantics 

In CONFIG_SMP=y kernels, smp_call_function_single() returns -ENXIO when
invoked for a non-existent CPU.  In contrast, in CONFIG_SMP=n kernels,
a splat is emitted and smp_call_function_single() otherwise silently
ignores its "cpu" argument, instead pretending that the caller intended
to have something happen on CPU 0.  Given that there is now code that
expects smp_call_function_single() to return an error if a bad CPU was
specified, this difference in semantics needs to be addressed.

Bring the semantics of the CONFIG_SMP=n version of
smp_call_function_single() into alignment with its CONFIG_SMP=y
counterpart.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200205143409.GA7021@paulmck-ThinkPad-P72
This commit is contained in:
Paul E. McKenney 2020-02-05 06:34:09 -08:00 committed by Thomas Gleixner
parent 25a3a15417
commit 1e474b28e7
1 changed files with 2 additions and 1 deletions
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3
kernel/up.c
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@ -14,7 +14,8 @@ int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
{
unsigned long flags;
WARN_ON(cpu != 0);
if (cpu != 0)
return -ENXIO;
local_irq_save(flags);
func(info);