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 <b...@kernel.crashing.org>
---
arch/powerpc/include/asm/smp.h | 1 +
arch/powerpc/kernel/head_32.S | 9 +++++++++
arch/powerpc/kernel/smp.c | 9 +++++++--
arch/powerpc/platforms/pseries/offline_states.h | 2 --
4 files changed, 17 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h
index 66e237b..1de0e97 100644
--- a/arch/powerpc/include/asm/smp.h
+++ b/arch/powerpc/include/asm/smp.h
@@ -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);
diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S
index 98c4b29..c5c24be 100644
--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -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
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 9813605..1c9956c 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -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
diff --git a/arch/powerpc/platforms/pseries/offline_states.h
b/arch/powerpc/platforms/pseries/offline_states.h
index 75a6f48..08672d9 100644
--- a/arch/powerpc/platforms/pseries/offline_states.h
+++ b/arch/powerpc/platforms/pseries/offline_states.h
@@ -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
--
1.7.1
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