tracing/hw-branch-tracing: convert bts-tracer mutex to a spinlock
Impact: fix CPU hotplug lockup bts_hotcpu_handler() is called with irqs disabled, so using mutex_lock() is a no-no. All the BTS codepaths here are atomic (they do not schedule), so using a spinlock is the right solution. Cc: Markus Metzger <markus.t.metzger@intel.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>hifive-unleashed-5.1
Ingo Molnar
parent
499aa86dcb
commit
2d542cf342
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@ -3,17 +3,15 @@
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*
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* Copyright (C) 2008-2009 Intel Corporation.
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* Markus Metzger <markus.t.metzger@gmail.com>, 2008-2009
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*
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*/
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#include <linux/module.h>
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#include <linux/fs.h>
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#include <linux/spinlock.h>
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#include <linux/kallsyms.h>
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#include <linux/debugfs.h>
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#include <linux/ftrace.h>
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#include <linux/kallsyms.h>
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#include <linux/mutex.h>
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#include <linux/module.h>
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#include <linux/cpu.h>
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#include <linux/smp.h>
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#include <linux/fs.h>
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#include <asm/ds.h>
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@ -23,16 +21,17 @@
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#define SIZEOF_BTS (1 << 13)
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/* The tracer mutex protects the below per-cpu tracer array.
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It needs to be held to:
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- start tracing on all cpus
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- stop tracing on all cpus
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- start tracing on a single hotplug cpu
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- stop tracing on a single hotplug cpu
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- read the trace from all cpus
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- read the trace from a single cpu
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*/
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static DEFINE_MUTEX(bts_tracer_mutex);
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/*
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* The tracer lock protects the below per-cpu tracer array.
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* It needs to be held to:
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* - start tracing on all cpus
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* - stop tracing on all cpus
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* - start tracing on a single hotplug cpu
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* - stop tracing on a single hotplug cpu
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* - read the trace from all cpus
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* - read the trace from a single cpu
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*/
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static DEFINE_SPINLOCK(bts_tracer_lock);
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static DEFINE_PER_CPU(struct bts_tracer *, tracer);
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static DEFINE_PER_CPU(unsigned char[SIZEOF_BTS], buffer);
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@ -47,7 +46,7 @@ static struct trace_array *hw_branch_trace __read_mostly;
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* Start tracing on the current cpu.
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* The argument is ignored.
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*
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* pre: bts_tracer_mutex must be locked.
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* pre: bts_tracer_lock must be locked.
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*/
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static void bts_trace_start_cpu(void *arg)
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{
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@ -66,19 +65,19 @@ static void bts_trace_start_cpu(void *arg)
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static void bts_trace_start(struct trace_array *tr)
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{
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mutex_lock(&bts_tracer_mutex);
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spin_lock(&bts_tracer_lock);
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on_each_cpu(bts_trace_start_cpu, NULL, 1);
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trace_hw_branches_enabled = 1;
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mutex_unlock(&bts_tracer_mutex);
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spin_unlock(&bts_tracer_lock);
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}
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/*
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* Stop tracing on the current cpu.
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* The argument is ignored.
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*
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* pre: bts_tracer_mutex must be locked.
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* pre: bts_tracer_lock must be locked.
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*/
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static void bts_trace_stop_cpu(void *arg)
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{
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@ -90,12 +89,12 @@ static void bts_trace_stop_cpu(void *arg)
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static void bts_trace_stop(struct trace_array *tr)
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{
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mutex_lock(&bts_tracer_mutex);
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spin_lock(&bts_tracer_lock);
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trace_hw_branches_enabled = 0;
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on_each_cpu(bts_trace_stop_cpu, NULL, 1);
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mutex_unlock(&bts_tracer_mutex);
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spin_unlock(&bts_tracer_lock);
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}
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static int __cpuinit bts_hotcpu_handler(struct notifier_block *nfb,
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@ -103,7 +102,7 @@ static int __cpuinit bts_hotcpu_handler(struct notifier_block *nfb,
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{
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unsigned int cpu = (unsigned long)hcpu;
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mutex_lock(&bts_tracer_mutex);
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spin_lock(&bts_tracer_lock);
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if (!trace_hw_branches_enabled)
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goto out;
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@ -119,7 +118,7 @@ static int __cpuinit bts_hotcpu_handler(struct notifier_block *nfb,
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}
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out:
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mutex_unlock(&bts_tracer_mutex);
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spin_unlock(&bts_tracer_lock);
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return NOTIFY_DONE;
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}
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@ -225,7 +224,7 @@ static void trace_bts_at(const struct bts_trace *trace, void *at)
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/*
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* Collect the trace on the current cpu and write it into the ftrace buffer.
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*
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* pre: bts_tracer_mutex must be locked
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* pre: bts_tracer_lock must be locked
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*/
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static void trace_bts_cpu(void *arg)
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{
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@ -261,11 +260,11 @@ out:
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static void trace_bts_prepare(struct trace_iterator *iter)
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{
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mutex_lock(&bts_tracer_mutex);
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spin_lock(&bts_tracer_lock);
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on_each_cpu(trace_bts_cpu, iter->tr, 1);
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mutex_unlock(&bts_tracer_mutex);
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spin_unlock(&bts_tracer_lock);
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}
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static void trace_bts_close(struct trace_iterator *iter)
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@ -275,11 +274,11 @@ static void trace_bts_close(struct trace_iterator *iter)
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void trace_hw_branch_oops(void)
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{
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mutex_lock(&bts_tracer_mutex);
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spin_lock(&bts_tracer_lock);
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trace_bts_cpu(hw_branch_trace);
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mutex_unlock(&bts_tracer_mutex);
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spin_unlock(&bts_tracer_lock);
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}
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struct tracer bts_tracer __read_mostly =
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