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powerpc/smp: soft-replugged CPUs must go back to start_secondary 

Various thing are torn down when a CPU is hot-unplugged. That CPU
is expected to go back to start_secondary when re-plugged to re
initialize everything, such as clock sources, maps, ...

Some implementations just return from cpu_die() callback
in the idle loop when the CPU is "re-plugged". This is not enough.

We fix it using a little asm trampoline which resets the stack
and calls back into start_secondary as if we were all fresh from
boot. The trampoline already existed on ppc64, but we add it for
ppc32

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Benjamin Herrenschmidt 2011-02-10 18:45:24 +11:00
parent 963e5d3b76
commit fa3f82c8bb
4 changed files with 17 additions and 4 deletions
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1
arch/powerpc/include/asm/smp.h
View File

@ -36,6 +36,7 @@ extern void cpu_die(void);
extern void smp_send_debugger_break(int cpu);
extern void smp_message_recv(int);
extern void start_secondary_resume(void);
DECLARE_PER_CPU(unsigned int, cpu_pvr);

9
arch/powerpc/kernel/head_32.S
View File

@ -890,6 +890,15 @@ __secondary_start:
mtspr SPRN_SRR1,r4
SYNC
RFI
_GLOBAL(start_secondary_resume)
/* Reset stack */
rlwinm r1,r1,0,0,(31-THREAD_SHIFT) /* current_thread_info() */
addi r1,r1,THREAD_SIZE-STACK_FRAME_OVERHEAD
li r3,0
std r3,0(r1) /* Zero the stack frame pointer */
bl start_secondary
b .
#endif /* CONFIG_SMP */
#ifdef CONFIG_KVM_BOOK3S_HANDLER

9
arch/powerpc/kernel/smp.c
View File

@ -502,7 +502,7 @@ static struct device_node *cpu_to_l2cache(int cpu)
}
/* Activate a secondary processor. */
int __devinit start_secondary(void *unused)
void __devinit start_secondary(void *unused)
{
unsigned int cpu = smp_processor_id();
struct device_node *l2_cache;
@ -558,7 +558,8 @@ int __devinit start_secondary(void *unused)
local_irq_enable();
cpu_idle();
return 0;
BUG();
}
int setup_profiling_timer(unsigned int multiplier)
@ -660,5 +661,9 @@ void cpu_die(void)
{
if (ppc_md.cpu_die)
ppc_md.cpu_die();
/* If we return, we re-enter start_secondary */
start_secondary_resume();
}
#endif

2
arch/powerpc/platforms/pseries/offline_states.h
View File

@ -34,6 +34,4 @@ static inline void set_default_offline_state(int cpu)
#endif
extern enum cpu_state_vals get_preferred_offline_state(int cpu);
extern int start_secondary(void);
extern void start_secondary_resume(void);
#endif