From mboxrd@z Thu Jan 1 00:00:00 1970 From: srivatsa.bhat@linux.vnet.ibm.com (Srivatsa S. Bhat) Date: Tue, 22 Jan 2013 13:13:47 +0530 Subject: [PATCH v5 39/45] powerpc: Use get/put_online_cpus_atomic() to prevent CPU offline In-Reply-To: <20130122073210.13822.50434.stgit@srivatsabhat.in.ibm.com> References: <20130122073210.13822.50434.stgit@srivatsabhat.in.ibm.com> Message-ID: <20130122074344.13822.45560.stgit@srivatsabhat.in.ibm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Once stop_machine() is gone from the CPU offline path, we won't be able to depend on preempt_disable() or local_irq_disable() to prevent CPUs from going offline from under us. Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going offline, while invoking from atomic context. Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: linuxppc-dev at lists.ozlabs.org Signed-off-by: Srivatsa S. Bhat --- arch/powerpc/mm/mmu_context_nohash.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/powerpc/mm/mmu_context_nohash.c b/arch/powerpc/mm/mmu_context_nohash.c index e779642..29f58cf 100644 --- a/arch/powerpc/mm/mmu_context_nohash.c +++ b/arch/powerpc/mm/mmu_context_nohash.c @@ -196,6 +196,7 @@ void switch_mmu_context(struct mm_struct *prev, struct mm_struct *next) /* No lockless fast path .. yet */ raw_spin_lock(&context_lock); + get_online_cpus_atomic(); pr_hard("[%d] activating context for mm @%p, active=%d, id=%d", cpu, next, next->context.active, next->context.id); @@ -279,6 +280,7 @@ void switch_mmu_context(struct mm_struct *prev, struct mm_struct *next) /* Flick the MMU and release lock */ pr_hardcont(" -> %d\n", id); set_context(id, next->pgd); + put_online_cpus_atomic(); raw_spin_unlock(&context_lock); }