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author | James Hogan <james.hogan@imgtec.com> | 2016-07-13 15:12:46 +0200 |
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committer | Ralf Baechle <ralf@linux-mips.org> | 2016-07-29 10:19:28 +0200 |
commit | 926963160ca4d6267957541a85591b7c426066d6 (patch) | |
tree | a610f9ed2b5b2cde966678f6d01943db7bb12612 | |
parent | MIPS: SMP: Update cpu_foreign_map on CPU disable (diff) | |
download | linux-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.c | 9 |
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(); |