Doorbell can be used to cause ipi on cpus which are sibling threads on
the same core. So icp_native_cause_ipi checks if the destination cpu
is a sibling thread of the current cpu and uses doorbell in such cases.
But while running with CONFIG_PREEMPT=y, since this section is
preemtible, we can run into issues if after we check if the destination
cpu is a sibling cpu, the task gets migrated from a sibling cpu to a
cpu on another core.
Fix this by using get_cpu()/ put_cpu()
Signed-off-by: Shreyas B. Prabhu <shre...@linux.vnet.ibm.com>
---
arch/powerpc/sysdev/xics/icp-native.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/sysdev/xics/icp-native.c
b/arch/powerpc/sysdev/xics/icp-native.c
index 2fc4cf1..62fd478 100644
--- a/arch/powerpc/sysdev/xics/icp-native.c
+++ b/arch/powerpc/sysdev/xics/icp-native.c
@@ -147,12 +147,16 @@ static void icp_native_cause_ipi(int cpu, unsigned long
data)
{
kvmppc_set_host_ipi(cpu, 1);
#ifdef CONFIG_PPC_DOORBELL
- if (cpu_has_feature(CPU_FTR_DBELL) &&
- (cpumask_test_cpu(cpu, cpu_sibling_mask(smp_processor_id()))))
- doorbell_cause_ipi(cpu, data);
- else
+ if (cpu_has_feature(CPU_FTR_DBELL)) {
+ if (cpumask_test_cpu(cpu, cpu_sibling_mask(get_cpu()))) {
+ doorbell_cause_ipi(cpu, data);
+ put_cpu();
+ return;
+ }
+ put_cpu();
+ }
#endif
- icp_native_set_qirr(cpu, IPI_PRIORITY);
+ icp_native_set_qirr(cpu, IPI_PRIORITY);
}
/*
--
1.9.3
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