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authorJames Hogan <james.hogan@imgtec.com>2016-07-13 15:12:46 +0200
committerRalf Baechle <ralf@linux-mips.org>2016-07-29 10:19:28 +0200
commit926963160ca4d6267957541a85591b7c426066d6 (patch)
treea610f9ed2b5b2cde966678f6d01943db7bb12612
parentMIPS: SMP: Update cpu_foreign_map on CPU disable (diff)
downloadlinux-926963160ca4d6267957541a85591b7c426066d6.tar.xz
linux-926963160ca4d6267957541a85591b7c426066d6.zip
MIPS: SMP: Drop stop_this_cpu() cpu_foreign_map hack
Commit cccf34e9411c ("MIPS: c-r4k: Fix cache flushing for MT cores") added the cpu_foreign_map cpumask containing a single VPE from each online core, and recalculated it when secondary CPUs are brought up. stop_this_cpu() was also updated to recalculate cpu_foreign_map, but with an additional hack before marking the CPU as offline to copy cpu_online_mask into cpu_foreign_map and perform an SMP memory barrier. This appears to have been intended to prevent cache management IPIs being missed when the VPE representing the core in cpu_foreign_map is taken offline while other VPEs remain online. Unfortunately there is nothing in this hack to prevent r4k_on_each_cpu() from reading the old cpu_foreign_map, and smp_call_function_many() from reading that new cpu_online_mask with the core's representative VPE marked offline. It then wouldn't send an IPI to any online VPEs of that core. stop_this_cpu() is only actually called in panic and system shutdown / halt / reboot situations, in which case all CPUs are going down and we don't really need to care about cache management, so drop this hack. Note that the __cpu_disable() case for CPU hotplug is handled in the previous commit, and no synchronisation is needed there due to the use of stop_machine() which prevents hotplug from taking place while any CPU has disabled preemption (as r4k_on_each_cpu() does). Signed-off-by: James Hogan <james.hogan@imgtec.com> Cc: Paul Burton <paul.burton@imgtec.com> Cc: Leonid Yegoshin <leonid.yegoshin@imgtec.com> Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/13796/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
-rw-r--r--arch/mips/kernel/smp.c9
1 files changed, 1 insertions, 8 deletions
diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c
index a4d4309ecff2..783d5f50ab9d 100644
--- a/arch/mips/kernel/smp.c
+++ b/arch/mips/kernel/smp.c
@@ -344,16 +344,9 @@ asmlinkage void start_secondary(void)
static void stop_this_cpu(void *dummy)
{
/*
- * Remove this CPU. Be a bit slow here and
- * set the bits for every online CPU so we don't miss
- * any IPI whilst taking this VPE down.
+ * Remove this CPU:
*/
- cpumask_copy(&cpu_foreign_map, cpu_online_mask);
-
- /* Make it visible to every other CPU */
- smp_mb();
-
set_cpu_online(smp_processor_id(), false);
calculate_cpu_foreign_map();
local_irq_disable();