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James Hogan authored
Commit cccf34e9 ("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>
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