On Wed, 2015-05-20 at 00:30 +0530, Shreyas B. Prabhu wrote:
> 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()
Thanks. Looks good and it's boots for me.
Signed-off-by: Michael Neuling <mi...@neuling.org>
> 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);
> }
>
> /*
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