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powerpc: Make doorbell check preemption safe

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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 <shreyas@linux.vnet.ibm.com>
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Shreyas B. Prabhu 2015-05-20 00:30:14 +05:30 committed by Michael Ellerman
parent 4bece972fc
commit 3609d819a3
1 changed files with 9 additions and 5 deletions
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14
arch/powerpc/sysdev/xics/icp-native.c
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@ -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);
}
/*