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powerpc: Reset kernel stack on cpu online from cede state 

Cpu hotplug (offline) without dlpar operation will place cpu
in cede state and the extended_cede_processor() function will
return when resumed.

Kernel stack pointer needs to be reset before
start_secondary() is called to continue the online operation.

Added new function start_secondary_resume() to do the above
steps.

Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Vaidyanathan Srinivasan 2010-03-01 02:58:09 +00:00 committed by Benjamin Herrenschmidt
parent de0b632ba0
commit 8dbce53cc2
3 changed files with 16 additions and 5 deletions
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11
arch/powerpc/kernel/head_64.S
View File

@ -617,6 +617,17 @@ _GLOBAL(start_secondary_prolog)
std r3,0(r1) /* Zero the stack frame pointer */
bl .start_secondary
b .
/*
* Reset stack pointer and call start_secondary
* to continue with online operation when woken up
* from cede in cpu offline.
*/
_GLOBAL(start_secondary_resume)
ld r1,PACAKSAVE(r13) /* Reload kernel stack pointer */
li r3,0
std r3,0(r1) /* Zero the stack frame pointer */
bl .start_secondary
b .
#endif
/*

9
arch/powerpc/platforms/pseries/hotplug-cpu.c
View File

@ -146,12 +146,11 @@ static void pseries_mach_cpu_die(void)
unregister_slb_shadow(hwcpu, __pa(get_slb_shadow()));
/*
* NOTE: Calling start_secondary() here for now to
* start new context.
* However, need to do it cleanly by resetting the
* stack pointer.
* Call to start_secondary_resume() will not return.
* Kernel stack will be reset and start_secondary()
* will be called to continue the online operation.
*/
start_secondary();
start_secondary_resume();
} else if (get_preferred_offline_state(cpu) == CPU_STATE_OFFLINE) {

1
arch/powerpc/platforms/pseries/offline_states.h
View File

@ -35,4 +35,5 @@ static inline void set_default_offline_state(int cpu)
extern enum cpu_state_vals get_preferred_offline_state(int cpu);
extern int start_secondary(void);
extern void start_secondary_resume(void);
#endif