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powerpc: Add optional smp_ops->prepare_cpu SMP callback

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Some platforms (will) need to perform allocations before bringing
a new CPU online. Doing it from smp_ops->setup_cpu is the wrong
thing to do:

 - It has no useful failure path (too late)
 - Calling any allocator will enable interrupts prematurely
   causing problems with large decrementer among others

Instead, add a new callback that is called from __cpu_up (so from
the context trying to online the new CPU) at a point where we
can safely allocate and handle failures.

This will be used by XIVE support.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Benjamin Herrenschmidt 2017-04-05 17:54:48 +10:00 committed by Michael Ellerman
parent 22bd64a621
commit 14d4ae5c4c
2 changed files with 11 additions and 0 deletions
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1
arch/powerpc/include/asm/smp.h
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@ -44,6 +44,7 @@ struct smp_ops_t {
#endif
void (*probe)(void);
int (*kick_cpu)(int nr);
int (*prepare_cpu)(int nr);
void (*setup_cpu)(int nr);
void (*bringup_done)(void);
void (*take_timebase)(void);

10
arch/powerpc/kernel/smp.c
View File

@ -521,6 +521,16 @@ int __cpu_up(unsigned int cpu, struct task_struct *tidle)
cpu_idle_thread_init(cpu, tidle);
/*
* The platform might need to allocate resources prior to bringing
* up the CPU
*/
if (smp_ops->prepare_cpu) {
rc = smp_ops->prepare_cpu(cpu);
if (rc)
return rc;
}
/* Make sure callin-map entry is 0 (can be leftover a CPU
* hotplug
*/