104 lines
3.5 KiB
Diff
104 lines
3.5 KiB
Diff
From e5d045de85238a504370b091160ef0eca67f6e90 Mon Sep 17 00:00:00 2001
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From: Mike Galbraith <umgwanakikbuti@gmail.com>
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Date: Fri, 2 May 2014 13:13:34 +0200
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Subject: [PATCH] stomp-machine: use lg_global_trylock_relax() to dead with
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stop_cpus_lock lglock
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.0/patches-4.0.5-rt3.tar.xz
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If the stop machinery is called from inactive CPU we cannot use
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lg_global_lock(), because some other stomp machine invocation might be
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in progress and the lock can be contended. We cannot schedule from this
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context, so use the lovely new lg_global_trylock_relax() primitive to
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do what we used to do via one mutex_trylock()/cpu_relax() loop. We
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now do that trylock()/relax() across an entire herd of locks. Joy.
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Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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kernel/stop_machine.c | 24 ++++++++++++++----------
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1 file changed, 14 insertions(+), 10 deletions(-)
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--- a/kernel/stop_machine.c
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+++ b/kernel/stop_machine.c
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@@ -266,7 +266,7 @@ int stop_two_cpus(unsigned int cpu1, uns
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struct irq_cpu_stop_queue_work_info call_args;
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struct multi_stop_data msdata;
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- preempt_disable();
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+ preempt_disable_nort();
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msdata = (struct multi_stop_data){
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.fn = fn,
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.data = arg,
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@@ -299,7 +299,7 @@ int stop_two_cpus(unsigned int cpu1, uns
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* This relies on the stopper workqueues to be FIFO.
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*/
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if (!cpu_active(cpu1) || !cpu_active(cpu2)) {
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- preempt_enable();
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+ preempt_enable_nort();
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return -ENOENT;
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}
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@@ -313,7 +313,7 @@ int stop_two_cpus(unsigned int cpu1, uns
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&irq_cpu_stop_queue_work,
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&call_args, 1);
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lg_local_unlock(&stop_cpus_lock);
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- preempt_enable();
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+ preempt_enable_nort();
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wait_for_stop_done(&done);
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@@ -347,7 +347,7 @@ static DEFINE_PER_CPU(struct cpu_stop_wo
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static void queue_stop_cpus_work(const struct cpumask *cpumask,
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cpu_stop_fn_t fn, void *arg,
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- struct cpu_stop_done *done)
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+ struct cpu_stop_done *done, bool inactive)
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{
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struct cpu_stop_work *work;
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unsigned int cpu;
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@@ -361,11 +361,13 @@ static void queue_stop_cpus_work(const s
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}
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/*
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- * Disable preemption while queueing to avoid getting
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- * preempted by a stopper which might wait for other stoppers
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- * to enter @fn which can lead to deadlock.
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+ * Make sure that all work is queued on all cpus before
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+ * any of the cpus can execute it.
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*/
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- lg_global_lock(&stop_cpus_lock);
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+ if (!inactive)
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+ lg_global_lock(&stop_cpus_lock);
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+ else
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+ lg_global_trylock_relax(&stop_cpus_lock);
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for_each_cpu(cpu, cpumask)
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cpu_stop_queue_work(cpu, &per_cpu(stop_cpus_work, cpu));
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lg_global_unlock(&stop_cpus_lock);
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@@ -377,7 +379,7 @@ static int __stop_cpus(const struct cpum
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struct cpu_stop_done done;
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cpu_stop_init_done(&done, cpumask_weight(cpumask));
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- queue_stop_cpus_work(cpumask, fn, arg, &done);
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+ queue_stop_cpus_work(cpumask, fn, arg, &done, false);
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wait_for_stop_done(&done);
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return done.executed ? done.ret : -ENOENT;
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}
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@@ -573,6 +575,8 @@ static int __init cpu_stop_init(void)
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INIT_LIST_HEAD(&stopper->works);
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}
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+ lg_lock_init(&stop_cpus_lock, "stop_cpus_lock");
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+
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BUG_ON(smpboot_register_percpu_thread(&cpu_stop_threads));
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stop_machine_initialized = true;
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return 0;
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@@ -668,7 +672,7 @@ int stop_machine_from_inactive_cpu(int (
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set_state(&msdata, MULTI_STOP_PREPARE);
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cpu_stop_init_done(&done, num_active_cpus());
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queue_stop_cpus_work(cpu_active_mask, multi_cpu_stop, &msdata,
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- &done);
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+ &done, true);
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ret = multi_cpu_stop(&msdata);
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/* Busy wait for completion. */
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