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 <[email protected]> --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
