3.16.79-rc1 review patch. If anyone has any objections, please let me know.
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From: Nathan Lynch nathanl@linux.ibm.com
commit 92c94dfb69e350471473fd3075c74bc68150879e upstream.
prep_irq_for_idle() is intended to be called before entering H_CEDE (and it is used by the pseries cpuidle driver). However the default pseries idle routine does not call it, leading to mismanaged lazy irq state when the cpuidle driver isn't in use. Manifestations of this include:
* Dropped IPIs in the time immediately after a cpu comes online (before it has installed the cpuidle handler), making the online operation block indefinitely waiting for the new cpu to respond.
* Hitting this WARN_ON in arch_local_irq_restore(): /* * We should already be hard disabled here. We had bugs * where that wasn't the case so let's dbl check it and * warn if we are wrong. Only do that when IRQ tracing * is enabled as mfmsr() can be costly. */ if (WARN_ON_ONCE(mfmsr() & MSR_EE)) __hard_irq_disable();
Call prep_irq_for_idle() from pseries_lpar_idle() and honor its result.
Fixes: 363edbe2614a ("powerpc: Default arch idle could cede processor on pseries") Signed-off-by: Nathan Lynch nathanl@linux.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20190910225244.25056-1-nathanl@linux.ibm.com Signed-off-by: Ben Hutchings ben@decadent.org.uk --- arch/powerpc/platforms/pseries/setup.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/arch/powerpc/platforms/pseries/setup.c +++ b/arch/powerpc/platforms/pseries/setup.c @@ -360,6 +360,9 @@ static void pseries_lpar_idle(void) * low power mode by cedeing processor to hypervisor */
+ if (!prep_irq_for_idle()) + return; + /* Indicate to hypervisor that we are idle. */ get_lppaca()->idle = 1;