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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 2009-02-25 08:40:09 +01:00
parent 499aa86dcb
commit 2d542cf342
1 changed files with 28 additions and 29 deletions
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55
kernel/trace/trace_hw_branches.c
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@ -3,17 +3,15 @@
* *
* Copyright (C) 2008-2009 Intel Corporation. * Copyright (C) 2008-2009 Intel Corporation.
* Markus Metzger <markus.t.metzger@gmail.com>, 2008-2009 * Markus Metzger <markus.t.metzger@gmail.com>, 2008-2009
*
*/ */
#include <linux/spinlock.h>
#include <linux/module.h> #include <linux/kallsyms.h>
#include <linux/fs.h>
#include <linux/debugfs.h> #include <linux/debugfs.h>
#include <linux/ftrace.h> #include <linux/ftrace.h>
#include <linux/kallsyms.h> #include <linux/module.h>
#include <linux/mutex.h>
#include <linux/cpu.h> #include <linux/cpu.h>
#include <linux/smp.h> #include <linux/smp.h>
#include <linux/fs.h>
#include <asm/ds.h> #include <asm/ds.h>
@ -23,16 +21,17 @@
#define SIZEOF_BTS (1 << 13) #define SIZEOF_BTS (1 << 13)
/* The tracer mutex protects the below per-cpu tracer array. /*
It needs to be held to: * The tracer lock protects the below per-cpu tracer array.
- start tracing on all cpus * It needs to be held to:
- stop tracing on all cpus * - start tracing on all cpus
- start tracing on a single hotplug cpu * - stop tracing on all cpus
- stop tracing on a single hotplug cpu * - start tracing on a single hotplug cpu
- read the trace from all cpus * - stop tracing on a single hotplug cpu
- read the trace from a single cpu * - read the trace from all cpus
* - read the trace from a single cpu
*/ */
static DEFINE_MUTEX(bts_tracer_mutex); static DEFINE_SPINLOCK(bts_tracer_lock);
static DEFINE_PER_CPU(struct bts_tracer *, tracer); static DEFINE_PER_CPU(struct bts_tracer *, tracer);
static DEFINE_PER_CPU(unsigned char[SIZEOF_BTS], buffer); static DEFINE_PER_CPU(unsigned char[SIZEOF_BTS], buffer);
@ -47,7 +46,7 @@ static struct trace_array *hw_branch_trace __read_mostly;
* Start tracing on the current cpu. * Start tracing on the current cpu.
* The argument is ignored. * The argument is ignored.
* *
* pre: bts_tracer_mutex must be locked. * pre: bts_tracer_lock must be locked.
*/ */
static void bts_trace_start_cpu(void *arg) static void bts_trace_start_cpu(void *arg)
{ {
@ -66,19 +65,19 @@ static void bts_trace_start_cpu(void *arg)
static void bts_trace_start(struct trace_array *tr) static void bts_trace_start(struct trace_array *tr)
{ {
mutex_lock(&bts_tracer_mutex); spin_lock(&bts_tracer_lock);
on_each_cpu(bts_trace_start_cpu, NULL, 1); on_each_cpu(bts_trace_start_cpu, NULL, 1);
trace_hw_branches_enabled = 1; trace_hw_branches_enabled = 1;
mutex_unlock(&bts_tracer_mutex); spin_unlock(&bts_tracer_lock);
} }
/* /*
* Stop tracing on the current cpu. * Stop tracing on the current cpu.
* The argument is ignored. * The argument is ignored.
* *
* pre: bts_tracer_mutex must be locked. * pre: bts_tracer_lock must be locked.
*/ */
static void bts_trace_stop_cpu(void *arg) static void bts_trace_stop_cpu(void *arg)
{ {
@ -90,12 +89,12 @@ static void bts_trace_stop_cpu(void *arg)
static void bts_trace_stop(struct trace_array *tr) static void bts_trace_stop(struct trace_array *tr)
{ {
mutex_lock(&bts_tracer_mutex); spin_lock(&bts_tracer_lock);
trace_hw_branches_enabled = 0; trace_hw_branches_enabled = 0;
on_each_cpu(bts_trace_stop_cpu, NULL, 1); on_each_cpu(bts_trace_stop_cpu, NULL, 1);
mutex_unlock(&bts_tracer_mutex); spin_unlock(&bts_tracer_lock);
} }
static int __cpuinit bts_hotcpu_handler(struct notifier_block *nfb, static int __cpuinit bts_hotcpu_handler(struct notifier_block *nfb,
@ -103,7 +102,7 @@ static int __cpuinit bts_hotcpu_handler(struct notifier_block *nfb,
{ {
unsigned int cpu = (unsigned long)hcpu; unsigned int cpu = (unsigned long)hcpu;
mutex_lock(&bts_tracer_mutex); spin_lock(&bts_tracer_lock);
if (!trace_hw_branches_enabled) if (!trace_hw_branches_enabled)
goto out; goto out;
@ -119,7 +118,7 @@ static int __cpuinit bts_hotcpu_handler(struct notifier_block *nfb,
} }
out: out:
mutex_unlock(&bts_tracer_mutex); spin_unlock(&bts_tracer_lock);
return NOTIFY_DONE; return NOTIFY_DONE;
} }
@ -225,7 +224,7 @@ static void trace_bts_at(const struct bts_trace *trace, void *at)
/* /*
* Collect the trace on the current cpu and write it into the ftrace buffer. * Collect the trace on the current cpu and write it into the ftrace buffer.
* *
* pre: bts_tracer_mutex must be locked * pre: bts_tracer_lock must be locked
*/ */
static void trace_bts_cpu(void *arg) static void trace_bts_cpu(void *arg)
{ {
@ -261,11 +260,11 @@ out:
static void trace_bts_prepare(struct trace_iterator *iter) static void trace_bts_prepare(struct trace_iterator *iter)
{ {
mutex_lock(&bts_tracer_mutex); spin_lock(&bts_tracer_lock);
on_each_cpu(trace_bts_cpu, iter->tr, 1); on_each_cpu(trace_bts_cpu, iter->tr, 1);
mutex_unlock(&bts_tracer_mutex); spin_unlock(&bts_tracer_lock);
} }
static void trace_bts_close(struct trace_iterator *iter) static void trace_bts_close(struct trace_iterator *iter)
@ -275,11 +274,11 @@ static void trace_bts_close(struct trace_iterator *iter)
void trace_hw_branch_oops(void) void trace_hw_branch_oops(void)
{ {
mutex_lock(&bts_tracer_mutex); spin_lock(&bts_tracer_lock);
trace_bts_cpu(hw_branch_trace); trace_bts_cpu(hw_branch_trace);
mutex_unlock(&bts_tracer_mutex); spin_unlock(&bts_tracer_lock);
} }
struct tracer bts_tracer __read_mostly = struct tracer bts_tracer __read_mostly =