This is a note to let you know that I've just added the patch titled
MIPS: SMP: Use a completion event to signal CPU up
to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: mips-smp-use-a-completion-event-to-signal-cpu-up.patch and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From a00eeede507c975087b7b8df8cf2c9f88ba285de Mon Sep 17 00:00:00 2001
From: Matt Redfearn matt.redfearn@imgtec.com Date: Fri, 4 Nov 2016 09:28:56 +0000 Subject: MIPS: SMP: Use a completion event to signal CPU up
From: Matt Redfearn matt.redfearn@imgtec.com
commit a00eeede507c975087b7b8df8cf2c9f88ba285de upstream.
If a secondary CPU failed to start, for any reason, the CPU requesting the secondary to start would get stuck in the loop waiting for the secondary to be present in the cpu_callin_map.
Rather than that, use a completion event to signal that the secondary CPU has started and is waiting to synchronise counters.
Since the CPU presence will no longer be marked in cpu_callin_map, remove the redundant test from arch_cpu_idle_dead().
Signed-off-by: Matt Redfearn matt.redfearn@imgtec.com Cc: Maciej W. Rozycki macro@imgtec.com Cc: Jiri Slaby jslaby@suse.cz Cc: Paul Gortmaker paul.gortmaker@windriver.com Cc: Chris Metcalf cmetcalf@mellanox.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Qais Yousef qsyousef@gmail.com Cc: James Hogan james.hogan@imgtec.com Cc: Paul Burton paul.burton@imgtec.com Cc: Marcin Nowakowski marcin.nowakowski@imgtec.com Cc: Andrew Morton akpm@linux-foundation.org Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/14502/ Signed-off-by: Ralf Baechle ralf@linux-mips.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/mips/kernel/process.c | 4 +--- arch/mips/kernel/smp.c | 15 +++++++++------ 2 files changed, 10 insertions(+), 9 deletions(-)
--- a/arch/mips/kernel/process.c +++ b/arch/mips/kernel/process.c @@ -49,9 +49,7 @@ #ifdef CONFIG_HOTPLUG_CPU void arch_cpu_idle_dead(void) { - /* What the heck is this check doing ? */ - if (!cpumask_test_cpu(smp_processor_id(), &cpu_callin_map)) - play_dead(); + play_dead(); } #endif
--- a/arch/mips/kernel/smp.c +++ b/arch/mips/kernel/smp.c @@ -64,6 +64,8 @@ EXPORT_SYMBOL(cpu_sibling_map); cpumask_t cpu_core_map[NR_CPUS] __read_mostly; EXPORT_SYMBOL(cpu_core_map);
+static DECLARE_COMPLETION(cpu_running); + /* * A logcal cpu mask containing only one VPE per core to * reduce the number of IPIs on large MT systems. @@ -174,7 +176,7 @@ asmlinkage void start_secondary(void) cpumask_set_cpu(cpu, &cpu_coherent_mask); notify_cpu_starting(cpu);
- cpumask_set_cpu(cpu, &cpu_callin_map); + complete(&cpu_running); synchronise_count_slave(cpu);
set_cpu_online(cpu, true); @@ -242,7 +244,6 @@ void smp_prepare_boot_cpu(void) { set_cpu_possible(0, true); set_cpu_online(0, true); - cpumask_set_cpu(0, &cpu_callin_map); }
int __cpu_up(unsigned int cpu, struct task_struct *tidle) @@ -250,11 +251,13 @@ int __cpu_up(unsigned int cpu, struct ta mp_ops->boot_secondary(cpu, tidle);
/* - * Trust is futile. We should really have timeouts ... + * We must check for timeout here, as the CPU will not be marked + * online until the counters are synchronised. */ - while (!cpumask_test_cpu(cpu, &cpu_callin_map)) { - udelay(100); - schedule(); + if (!wait_for_completion_timeout(&cpu_running, + msecs_to_jiffies(1000))) { + pr_crit("CPU%u: failed to start\n", cpu); + return -EIO; }
synchronise_count_master(cpu);
Patches currently in stable-queue which might be from matt.redfearn@imgtec.com are
queue-4.4/mips-smp-fix-deadlock-online-race.patch queue-4.4/mips-smp-use-a-completion-event-to-signal-cpu-up.patch