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powerpc: NMI IPI make NMI IPIs fully sychronous

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There is an asynchronous aspect to smp_send_nmi_ipi. The caller waits
for all CPUs to call in to the handler, but it does not wait for
completion of the handler. This is a needless complication, so remove
it and always wait synchronously.

The synchronous wait allows the caller to easily time out and clear
the wait for completion (zero nmi_ipi_busy_count) in the case of badly
behaved handlers. This would have prevented the recent smp_send_stop
NMI IPI bug from causing the system to hang.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Nicholas Piggin
2018-04-25 15:17:59 +10:00
committed by Michael Ellerman
parent 9b81c0211c
commit 5b73151fff
3 changed files with 27 additions and 25 deletions
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1
arch/powerpc/include/asm/smp.h
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@@ -56,7 +56,6 @@ struct smp_ops_t {
int (*cpu_bootable)(unsigned int nr);
};
extern void smp_flush_nmi_ipi(u64 delay_us);
extern int smp_send_nmi_ipi(int cpu, void (*fn)(struct pt_regs *), u64 delay_us);
extern int smp_send_safe_nmi_ipi(int cpu, void (*fn)(struct pt_regs *), u64 delay_us);
extern void smp_send_debugger_break(void);