[patch 07/18] x86, bts, hw-branch-tracer: add _noirq variants to the debug store interface

markus.t.metzger
2009-04-02T15:02:22Z

[-- Attachment #1: tip.master.ds.request_cpu.patch --]
[-- Type: text/plain, Size: 32042 bytes --]

The hw-branch-tracer uses debug store functions from an on_each_cpu()
context, which is simply wrong since the functions may sleep.

Add _noirq variants for most functions, which may be called with
interrupts disabled.

Separate per-cpu and per-task tracing and allow per-cpu tracing to be
controlled from any cpu.

Make the hw-branch-tracer use the new debug store interface, synchronize
with hotplug cpu event using get/put_online_cpus(), and remove the
unnecessary spinlock.

Make the ptrace bts and the ds selftest code use the new interface.

Defer the ds selftest.

Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
---
arch/x86/include/asm/ds.h | 57 45 + 12 - 0 !
arch/x86/kernel/ds.c | 474 367 + 107 - 0 !
arch/x86/kernel/ds_selftest.c | 9 5 + 4 - 0 !
arch/x86/kernel/ptrace.c | 5 3 + 2 - 0 !
kernel/trace/trace_hw_branches.c | 193 72 + 121 - 0 !
5 files changed, 492 insertions(+), 246 deletions(-)

Index: b/arch/x86/include/asm/ds.h
===================================================================
--- a/arch/x86/include/asm/ds.h
+++ b/arch/x86/include/asm/ds.h
@@ -15,8 +15,8 @@
* - buffer allocation (memory accounting)
*
*
- * Copyright (C) 2007-2008 Intel Corporation.
- * Markus Metzger <markus.t.metzger@intel.com>, 2007-2008
+ * Copyright (C) 2007-2009 Intel Corporation.
+ * Markus Metzger <markus.t.metzger@intel.com>, 2007-2009
*/

#ifndef _ASM_X86_DS_H
@@ -83,8 +83,10 @@ enum ds_feature {
* The interrupt threshold is independent from the overflow callback
* to allow users to use their own overflow interrupt handling mechanism.
*
- * task: the task to request recording for;
- * NULL for per-cpu recording on the current cpu
+ * The function might sleep.
+ *
+ * task: the task to request recording for
+ * cpu: the cpu to request recording for
* base: the base pointer for the (non-pageable) buffer;
* size: the size of the provided buffer in bytes
* ovfl: pointer to a function to be called on buffer overflow;
@@ -93,19 +95,28 @@ enum ds_feature {
* -1 if no interrupt threshold is requested.
* flags: a bit-mask of the above flags
*/
-extern struct bts_tracer *ds_request_bts(struct task_struct *task,
- void *base, size_t size,
- bts_ovfl_callback_t ovfl,
- size_t th, unsigned int flags);
-extern struct pebs_tracer *ds_request_pebs(struct task_struct *task,
- void *base, size_t size,
- pebs_ovfl_callback_t ovfl,
- size_t th, unsigned int flags);
+extern struct bts_tracer *ds_request_bts_task(struct task_struct *task,
+ void *base, size_t size,
+ bts_ovfl_callback_t ovfl,
+ size_t th, unsigned int flags);
+extern struct bts_tracer *ds_request_bts_cpu(int cpu, void *base, size_t size,
+ bts_ovfl_callback_t ovfl,
+ size_t th, unsigned int flags);
+extern struct pebs_tracer *ds_request_pebs_task(struct task_struct *task,
+ void *base, size_t size,
+ pebs_ovfl_callback_t ovfl,
+ size_t th, unsigned int flags);
+extern struct pebs_tracer *ds_request_pebs_cpu(int cpu,
+ void *base, size_t size,
+ pebs_ovfl_callback_t ovfl,
+ size_t th, unsigned int flags);

/*
* Release BTS or PEBS resources
* Suspend and resume BTS or PEBS tracing
*
+ * Must be called with irq's enabled.
+ *
* tracer: the tracer handle returned from ds_request_~()
*/
extern void ds_release_bts(struct bts_tracer *tracer);
@@ -115,6 +126,28 @@ extern void ds_release_pebs(struct pebs_
extern void ds_suspend_pebs(struct pebs_tracer *tracer);
extern void ds_resume_pebs(struct pebs_tracer *tracer);

+/*
+ * Release BTS or PEBS resources
+ * Suspend and resume BTS or PEBS tracing
+ *
+ * Cpu tracers must call this on the traced cpu.
+ * Task tracers must call ds_release_~_noirq() for themselves.
+ *
+ * May be called with irq's disabled.
+ *
+ * Returns 0 if successful;
+ * -EPERM if the cpu tracer does not trace the current cpu.
+ * -EPERM if the task tracer does not trace itself.
+ *
+ * tracer: the tracer handle returned from ds_request_~()
+ */
+extern int ds_release_bts_noirq(struct bts_tracer *tracer);
+extern int ds_suspend_bts_noirq(struct bts_tracer *tracer);
+extern int ds_resume_bts_noirq(struct bts_tracer *tracer);
+extern int ds_release_pebs_noirq(struct pebs_tracer *tracer);
+extern int ds_suspend_pebs_noirq(struct pebs_tracer *tracer);
+extern int ds_resume_pebs_noirq(struct pebs_tracer *tracer);
+

/*
* The raw DS buffer state as it is used for BTS and PEBS recording.
Index: b/arch/x86/kernel/ds.c
===================================================================
--- a/arch/x86/kernel/ds.c
+++ b/arch/x86/kernel/ds.c
@@ -244,18 +244,19 @@ struct ds_context {
struct pebs_tracer *pebs_master;

/* Use count: */
- unsigned long count;
+ unsigned long count;

/* Pointer to the context pointer field: */
struct ds_context **this;

- /* The traced task; NULL for current cpu: */
+ /* The traced task; NULL for cpu tracing: */
struct task_struct *task;
-};

-static DEFINE_PER_CPU(struct ds_context *, system_context_array);
+ /* The traced cpu; only valid if task is NULL: */
+ int cpu;
+};

-#define system_context per_cpu(system_context_array, smp_processor_id())
+static DEFINE_PER_CPU(struct ds_context *, cpu_context);

/*
@@ -292,46 +293,35 @@ static void wait_to_unschedule(struct ta
}
}

-static inline struct ds_context *ds_get_context(struct task_struct *task)
+static struct ds_context *ds_get_context(struct task_struct *task, int cpu)
{
struct ds_context **p_context =
- (task ? &task->thread.ds_ctx : &system_context);
+ (task ? &task->thread.ds_ctx : &per_cpu(cpu_context, cpu));
struct ds_context *context = NULL;
struct ds_context *new_context = NULL;
- unsigned long irq;

- /*
- * Chances are small that we already have a context.
- *
- * Contexts for per-cpu tracing are allocated using
- * smp_call_function(). We must not sleep.
- */
- new_context = kzalloc(sizeof(*new_context), GFP_ATOMIC);
+ /* Chances are small that we already have a context. */
+ new_context = kzalloc(sizeof(*new_context), GFP_KERNEL);
if (!new_context)
return NULL;

- spin_lock_irqsave(&ds_lock, irq);
+ spin_lock_irq(&ds_lock);

context = *p_context;
- if (!context) {
+ if (likely(!context)) {
context = new_context;

context->this = p_context;
context->task = task;
+ context->cpu = cpu;
context->count = 0;

- if (task)
- set_tsk_thread_flag(task, TIF_DS_AREA_MSR);
-
- if (!task || (task == current))
- wrmsrl(MSR_IA32_DS_AREA, (unsigned long)context->ds);
-
*p_context = context;
}

context->count++;

- spin_unlock_irqrestore(&ds_lock, irq);
+ spin_unlock_irq(&ds_lock);

if (context != new_context)
kfree(new_context);
@@ -339,7 +329,7 @@ static inline struct ds_context *ds_get_
return context;
}

-static inline void ds_put_context(struct ds_context *context)
+static void ds_put_context(struct ds_context *context)
{
unsigned long irq;

@@ -358,8 +348,15 @@ static inline void ds_put_context(struct
if (context->task)
clear_tsk_thread_flag(context->task, TIF_DS_AREA_MSR);

- if (!context->task || (context->task == current))
- wrmsrl(MSR_IA32_DS_AREA, 0);
+ /*
+ * We leave the (now dangling) pointer to the DS configuration in
+ * the DS_AREA msr. This is as good or as bad as replacing it with
+ * NULL - the hardware would crash if we enabled tracing.
+ *
+ * This saves us some problems with having to write an msr on a
+ * different cpu while preventing others from doing the same for the
+ * next context for that same cpu.
+ */

spin_unlock_irqrestore(&ds_lock, irq);

@@ -369,6 +366,31 @@ static inline void ds_put_context(struct
kfree(context);
}

+static void ds_install_ds_area(struct ds_context *context)
+{
+ unsigned long ds;
+
+ ds = (unsigned long)context->ds;
+
+ /*
+ * There is a race between the bts master and the pebs master.
+ *
+ * The thread/cpu access is synchronized via get/put_cpu() for
+ * task tracing and via wrmsr_on_cpu for cpu tracing.
+ *
+ * If bts and pebs are collected for the same task or same cpu,
+ * the same confiuration is written twice.
+ */
+ if (context->task) {
+ get_cpu();
+ if (context->task == current)
+ wrmsrl(MSR_IA32_DS_AREA, ds);
+ set_tsk_thread_flag(context->task, TIF_DS_AREA_MSR);
+ put_cpu();
+ } else
+ wrmsr_on_cpu(context->cpu, MSR_IA32_DS_AREA,
+ (u32)((u64)ds), (u32)((u64)ds >> 32));
+}

/*
* Call the tracer's callback on a buffer overflow.
@@ -651,6 +673,7 @@ static void ds_init_ds_trace(struct ds_t
* The value for 'no threshold' is -1, which will set the
* threshold outside of the buffer, just like we want it.
*/
+ ith *= ds_cfg.sizeof_rec[qual];
trace->ith = (void *)(buffer + size - ith);

trace->flags = flags;
@@ -659,7 +682,7 @@ static void ds_init_ds_trace(struct ds_t

static int ds_request(struct ds_tracer *tracer, struct ds_trace *trace,
enum ds_qualifier qual, struct task_struct *task,
- void *base, size_t size, size_t th, unsigned int flags)
+ int cpu, void *base, size_t size, size_t th)
{
struct ds_context *context;
int error;
@@ -672,7 +695,7 @@ static int ds_request(struct ds_tracer *
if (!base)
goto out;

- /* We require some space to do alignment adjustments below. */
+ /* We need space for alignment adjustments in ds_init_ds_trace(). */
error = -EINVAL;
if (size < (DS_ALIGNMENT + ds_cfg.sizeof_rec[qual]))
goto out;
@@ -689,25 +712,27 @@ static int ds_request(struct ds_tracer *
tracer->size = size;

error = -ENOMEM;
- context = ds_get_context(task);
+ context = ds_get_context(task, cpu);
if (!context)
goto out;
tracer->context = context;

- ds_init_ds_trace(trace, qual, base, size, th, flags);
+ /*
+ * Defer any tracer-specific initialization work for the context until
+ * context ownership has been clarified.
+ */

error = 0;
out:
return error;
}

-struct bts_tracer *ds_request_bts(struct task_struct *task,
- void *base, size_t size,
- bts_ovfl_callback_t ovfl, size_t th,
- unsigned int flags)
+static struct bts_tracer *ds_request_bts(struct task_struct *task, int cpu,
+ void *base, size_t size,
+ bts_ovfl_callback_t ovfl, size_t th,
+ unsigned int flags)
{
struct bts_tracer *tracer;
- unsigned long irq;
int error;

/* Buffer overflow notification is not yet implemented. */
@@ -719,42 +744,46 @@ struct bts_tracer *ds_request_bts(struct
if (error < 0)
goto out;

- /*
- * Per-cpu tracing is typically requested using smp_call_function().
- * We must not sleep.
- */
error = -ENOMEM;
- tracer = kzalloc(sizeof(*tracer), GFP_ATOMIC);
+ tracer = kzalloc(sizeof(*tracer), GFP_KERNEL);
if (!tracer)
goto out_put_tracer;
tracer->ovfl = ovfl;

+ /* Do some more error checking and acquire a tracing context. */
error = ds_request(&tracer->ds, &tracer->trace.ds,
- ds_bts, task, base, size, th, flags);
+ ds_bts, task, cpu, base, size, th);
if (error < 0)
goto out_tracer;

-
- spin_lock_irqsave(&ds_lock, irq);
+ /* Claim the bts part of the tracing context we acquired above. */
+ spin_lock_irq(&ds_lock);

error = -EPERM;
if (tracer->ds.context->bts_master)
goto out_unlock;
tracer->ds.context->bts_master = tracer;

- spin_unlock_irqrestore(&ds_lock, irq);
+ spin_unlock_irq(&ds_lock);

+ /*
+ * Now that we own the bts part of the context, let's complete the
+ * initialization for that part.
+ */
+ ds_init_ds_trace(&tracer->trace.ds, ds_bts, base, size, th, flags);
+ ds_write_config(tracer->ds.context, &tracer->trace.ds, ds_bts);
+ ds_install_ds_area(tracer->ds.context);

tracer->trace.read = bts_read;
tracer->trace.write = bts_write;

- ds_write_config(tracer->ds.context, &tracer->trace.ds, ds_bts);
+ /* Start tracing. */
ds_resume_bts(tracer);

return tracer;

out_unlock:
- spin_unlock_irqrestore(&ds_lock, irq);
+ spin_unlock_irq(&ds_lock);
ds_put_context(tracer->ds.context);
out_tracer:
kfree(tracer);
@@ -764,13 +793,27 @@ struct bts_tracer *ds_request_bts(struct
return ERR_PTR(error);
}

-struct pebs_tracer *ds_request_pebs(struct task_struct *task,
- void *base, size_t size,
- pebs_ovfl_callback_t ovfl, size_t th,
- unsigned int flags)
+struct bts_tracer *ds_request_bts_task(struct task_struct *task,
+ void *base, size_t size,
+ bts_ovfl_callback_t ovfl,
+ size_t th, unsigned int flags)
+{
+ return ds_request_bts(task, 0, base, size, ovfl, th, flags);
+}
+
+struct bts_tracer *ds_request_bts_cpu(int cpu, void *base, size_t size,
+ bts_ovfl_callback_t ovfl,
+ size_t th, unsigned int flags)
+{
+ return ds_request_bts(NULL, cpu, base, size, ovfl, th, flags);
+}
+
+static struct pebs_tracer *ds_request_pebs(struct task_struct *task, int cpu,
+ void *base, size_t size,
+ pebs_ovfl_callback_t ovfl, size_t th,
+ unsigned int flags)
{
struct pebs_tracer *tracer;
- unsigned long irq;
int error;

/* Buffer overflow notification is not yet implemented. */
@@ -782,37 +825,43 @@ struct pebs_tracer *ds_request_pebs(stru
if (error < 0)
goto out;

- /*
- * Per-cpu tracing is typically requested using smp_call_function().
- * We must not sleep.
- */
error = -ENOMEM;
- tracer = kzalloc(sizeof(*tracer), GFP_ATOMIC);
+ tracer = kzalloc(sizeof(*tracer), GFP_KERNEL);
if (!tracer)
goto out_put_tracer;
tracer->ovfl = ovfl;

+ /* Do some more error checking and acquire a tracing context. */
error = ds_request(&tracer->ds, &tracer->trace.ds,
- ds_pebs, task, base, size, th, flags);
+ ds_pebs, task, cpu, base, size, th);
if (error < 0)
goto out_tracer;

- spin_lock_irqsave(&ds_lock, irq);
+ /* Claim the pebs part of the tracing context we acquired above. */
+ spin_lock_irq(&ds_lock);

error = -EPERM;
if (tracer->ds.context->pebs_master)
goto out_unlock;
tracer->ds.context->pebs_master = tracer;

- spin_unlock_irqrestore(&ds_lock, irq);
+ spin_unlock_irq(&ds_lock);

+ /*
+ * Now that we own the pebs part of the context, let's complete the
+ * initialization for that part.
+ */
+ ds_init_ds_trace(&tracer->trace.ds, ds_pebs, base, size, th, flags);
ds_write_config(tracer->ds.context, &tracer->trace.ds, ds_pebs);
+ ds_install_ds_area(tracer->ds.context);
+
+ /* Start tracing. */
ds_resume_pebs(tracer);

return tracer;

out_unlock:
- spin_unlock_irqrestore(&ds_lock, irq);
+ spin_unlock_irq(&ds_lock);
ds_put_context(tracer->ds.context);
out_tracer:
kfree(tracer);
@@ -822,16 +871,26 @@ struct pebs_tracer *ds_request_pebs(stru
return ERR_PTR(error);
}

-void ds_release_bts(struct bts_tracer *tracer)
+struct pebs_tracer *ds_request_pebs_task(struct task_struct *task,
+ void *base, size_t size,
+ pebs_ovfl_callback_t ovfl,
+ size_t th, unsigned int flags)
{
- struct task_struct *task;
+ return ds_request_pebs(task, 0, base, size, ovfl, th, flags);
+}

- if (!tracer)
- return;
+struct pebs_tracer *ds_request_pebs_cpu(int cpu, void *base, size_t size,
+ pebs_ovfl_callback_t ovfl,
+ size_t th, unsigned int flags)
+{
+ return ds_request_pebs(NULL, cpu, base, size, ovfl, th, flags);
+}

- task = tracer->ds.context->task;
+static void ds_free_bts(struct bts_tracer *tracer)
+{
+ struct task_struct *task;

- ds_suspend_bts(tracer);
+ task = tracer->ds.context->task;

WARN_ON_ONCE(tracer->ds.context->bts_master != tracer);
tracer->ds.context->bts_master = NULL;
@@ -845,9 +904,69 @@ void ds_release_bts(struct bts_tracer *t
kfree(tracer);
}

+void ds_release_bts(struct bts_tracer *tracer)
+{
+ might_sleep();
+
+ if (!tracer)
+ return;
+
+ ds_suspend_bts(tracer);
+ ds_free_bts(tracer);
+}
+
+int ds_release_bts_noirq(struct bts_tracer *tracer)
+{
+ struct task_struct *task;
+ unsigned long irq;
+ int error;
+
+ if (!tracer)
+ return 0;
+
+ task = tracer->ds.context->task;
+
+ local_irq_save(irq);
+
+ error = -EPERM;
+ if (!task &&
+ (tracer->ds.context->cpu != smp_processor_id()))
+ goto out;
+
+ error = -EPERM;
+ if (task && (task != current))
+ goto out;
+
+ ds_suspend_bts_noirq(tracer);
+ ds_free_bts(tracer);
+
+ error = 0;
+ out:
+ local_irq_restore(irq);
+ return error;
+}
+
+static void update_task_debugctlmsr(struct task_struct *task,
+ unsigned long debugctlmsr)
+{
+ task->thread.debugctlmsr = debugctlmsr;
+
+ get_cpu();
+ if (task == current)
+ update_debugctlmsr(debugctlmsr);
+
+ if (task->thread.debugctlmsr)
+ set_tsk_thread_flag(task, TIF_DEBUGCTLMSR);
+ else
+ clear_tsk_thread_flag(task, TIF_DEBUGCTLMSR);
+ put_cpu();
+}
+
void ds_suspend_bts(struct bts_tracer *tracer)
{
struct task_struct *task;
+ unsigned long debugctlmsr;
+ int cpu;

if (!tracer)
return;
@@ -855,29 +974,60 @@ void ds_suspend_bts(struct bts_tracer *t
tracer->flags = 0;

task = tracer->ds.context->task;
+ cpu = tracer->ds.context->cpu;

- if (!task || (task == current))
- update_debugctlmsr(get_debugctlmsr() & ~BTS_CONTROL);
+ WARN_ON(!task && irqs_disabled());

- if (task) {
- task->thread.debugctlmsr &= ~BTS_CONTROL;
+ debugctlmsr = (task ?
+ task->thread.debugctlmsr :
+ get_debugctlmsr_on_cpu(cpu));
+ debugctlmsr &= ~BTS_CONTROL;

- if (!task->thread.debugctlmsr)
- clear_tsk_thread_flag(task, TIF_DEBUGCTLMSR);
- }
+ if (task)
+ update_task_debugctlmsr(task, debugctlmsr);
+ else
+ update_debugctlmsr_on_cpu(cpu, debugctlmsr);
}

-void ds_resume_bts(struct bts_tracer *tracer)
+int ds_suspend_bts_noirq(struct bts_tracer *tracer)
{
struct task_struct *task;
- unsigned long control;
+ unsigned long debugctlmsr, irq;
+ int cpu, error = 0;

if (!tracer)
- return;
+ return 0;

- tracer->flags = tracer->trace.ds.flags;
+ tracer->flags = 0;

task = tracer->ds.context->task;
+ cpu = tracer->ds.context->cpu;
+
+ local_irq_save(irq);
+
+ error = -EPERM;
+ if (!task && (cpu != smp_processor_id()))
+ goto out;
+
+ debugctlmsr = (task ?
+ task->thread.debugctlmsr :
+ get_debugctlmsr());
+ debugctlmsr &= ~BTS_CONTROL;
+
+ if (task)
+ update_task_debugctlmsr(task, debugctlmsr);
+ else
+ update_debugctlmsr(debugctlmsr);
+
+ error = 0;
+ out:
+ local_irq_restore(irq);
+ return error;
+}
+
+static unsigned long ds_bts_control(struct bts_tracer *tracer)
+{
+ unsigned long control;

control = ds_cfg.ctl[dsf_bts];
if (!(tracer->trace.ds.flags & BTS_KERNEL))
@@ -885,25 +1035,77 @@ void ds_resume_bts(struct bts_tracer *tr
if (!(tracer->trace.ds.flags & BTS_USER))
control |= ds_cfg.ctl[dsf_bts_user];

- if (task) {
- task->thread.debugctlmsr |= control;
- set_tsk_thread_flag(task, TIF_DEBUGCTLMSR);
- }
-
- if (!task || (task == current))
- update_debugctlmsr(get_debugctlmsr() | control);
+ return control;
}

-void ds_release_pebs(struct pebs_tracer *tracer)
+void ds_resume_bts(struct bts_tracer *tracer)
{
struct task_struct *task;
+ unsigned long debugctlmsr;
+ int cpu;

if (!tracer)
return;

+ tracer->flags = tracer->trace.ds.flags;
+
task = tracer->ds.context->task;
+ cpu = tracer->ds.context->cpu;

- ds_suspend_pebs(tracer);
+ WARN_ON(!task && irqs_disabled());
+
+ debugctlmsr = (task ?
+ task->thread.debugctlmsr :
+ get_debugctlmsr_on_cpu(cpu));
+ debugctlmsr |= ds_bts_control(tracer);
+
+ if (task)
+ update_task_debugctlmsr(task, debugctlmsr);
+ else
+ update_debugctlmsr_on_cpu(cpu, debugctlmsr);
+}
+
+int ds_resume_bts_noirq(struct bts_tracer *tracer)
+{
+ struct task_struct *task;
+ unsigned long debugctlmsr, irq;
+ int cpu, error = 0;
+
+ if (!tracer)
+ return 0;
+
+ tracer->flags = tracer->trace.ds.flags;
+
+ task = tracer->ds.context->task;
+ cpu = tracer->ds.context->cpu;
+
+ local_irq_save(irq);
+
+ error = -EPERM;
+ if (!task && (cpu != smp_processor_id()))
+ goto out;
+
+ debugctlmsr = (task ?
+ task->thread.debugctlmsr :
+ get_debugctlmsr());
+ debugctlmsr |= ds_bts_control(tracer);
+
+ if (task)
+ update_task_debugctlmsr(task, debugctlmsr);
+ else
+ update_debugctlmsr(debugctlmsr);
+
+ error = 0;
+ out:
+ local_irq_restore(irq);
+ return error;
+}
+
+static void ds_free_pebs(struct pebs_tracer *tracer)
+{
+ struct task_struct *task;
+
+ task = tracer->ds.context->task;

WARN_ON_ONCE(tracer->ds.context->pebs_master != tracer);
tracer->ds.context->pebs_master = NULL;
@@ -914,16 +1116,68 @@ void ds_release_pebs(struct pebs_tracer
kfree(tracer);
}

+void ds_release_pebs(struct pebs_tracer *tracer)
+{
+ might_sleep();
+
+ if (!tracer)
+ return;
+
+ ds_suspend_pebs(tracer);
+ ds_free_pebs(tracer);
+}
+
+int ds_release_pebs_noirq(struct pebs_tracer *tracer)
+{
+ struct task_struct *task;
+ unsigned long irq;
+ int error;
+
+ if (!tracer)
+ return 0;
+
+ task = tracer->ds.context->task;
+
+ local_irq_save(irq);
+
+ error = -EPERM;
+ if (!task &&
+ (tracer->ds.context->cpu != smp_processor_id()))
+ goto out;
+
+ error = -EPERM;
+ if (task && (task != current))
+ goto out;
+
+ ds_suspend_pebs_noirq(tracer);
+ ds_free_pebs(tracer);
+
+ error = 0;
+ out:
+ local_irq_restore(irq);
+ return error;
+}
+
void ds_suspend_pebs(struct pebs_tracer *tracer)
{

}

+int ds_suspend_pebs_noirq(struct pebs_tracer *tracer)
+{
+ return 0;
+}
+
void ds_resume_pebs(struct pebs_tracer *tracer)
{

}

+int ds_resume_pebs_noirq(struct pebs_tracer *tracer)
+{
+ return 0;
+}
+
const struct bts_trace *ds_read_bts(struct bts_tracer *tracer)
{
if (!tracer)
@@ -1032,26 +1286,6 @@ ds_configure(const struct ds_configurati
printk(KERN_INFO "[ds] pebs not available\n");
}

- if (ds_cfg.sizeof_rec[ds_bts]) {
- int error;
-
- error = ds_selftest_bts();
- if (error) {
- WARN(1, "[ds] selftest failed. disabling bts.\n");
- ds_cfg.sizeof_rec[ds_bts] = 0;
- }
- }
-
- if (ds_cfg.sizeof_rec[ds_pebs]) {
- int error;
-
- error = ds_selftest_pebs();
- if (error) {
- WARN(1, "[ds] selftest failed. disabling pebs.\n");
- ds_cfg.sizeof_rec[ds_pebs] = 0;
- }
- }
-
printk(KERN_INFO "[ds] sizes: address: %u bit, ",
8 * ds_cfg.sizeof_ptr_field);
printk("bts/pebs record: %u/%u bytes\n",
@@ -1149,3 +1383,29 @@ void ds_copy_thread(struct task_struct *
void ds_exit_thread(struct task_struct *tsk)
{
}
+
+static __init int ds_selftest(void)
+{
+ if (ds_cfg.sizeof_rec[ds_bts]) {
+ int error;
+
+ error = ds_selftest_bts();
+ if (error) {
+ WARN(1, "[ds] selftest failed. disabling bts.\n");
+ ds_cfg.sizeof_rec[ds_bts] = 0;
+ }
+ }
+
+ if (ds_cfg.sizeof_rec[ds_pebs]) {
+ int error;
+
+ error = ds_selftest_pebs();
+ if (error) {
+ WARN(1, "[ds] selftest failed. disabling pebs.\n");
+ ds_cfg.sizeof_rec[ds_pebs] = 0;
+ }
+ }
+
+ return 0;
+}
+device_initcall(ds_selftest);
Index: b/kernel/trace/trace_hw_branches.c
===================================================================
--- a/kernel/trace/trace_hw_branches.c
+++ b/kernel/trace/trace_hw_branches.c
@@ -4,7 +4,6 @@
* Copyright (C) 2008-2009 Intel Corporation.
* Markus Metzger <markus.t.metzger@gmail.com>, 2008-2009
*/
-#include <linux/spinlock.h>
#include <linux/kallsyms.h>
#include <linux/debugfs.h>
#include <linux/ftrace.h>
@@ -21,168 +20,113 @@

#define BTS_BUFFER_SIZE (1 << 13)

-/*
- * The tracer lock protects the below per-cpu tracer array.
- * It needs to be held to:
- * - start tracing on all cpus
- * - stop tracing on all cpus
- * - start tracing on a single hotplug cpu
- * - stop tracing on a single hotplug cpu
- * - read the trace from all cpus
- * - read the trace from a single cpu
- */
-static DEFINE_SPINLOCK(bts_tracer_lock);
static DEFINE_PER_CPU(struct bts_tracer *, tracer);
static DEFINE_PER_CPU(unsigned char[BTS_BUFFER_SIZE], buffer);

#define this_tracer per_cpu(tracer, smp_processor_id())
-#define this_buffer per_cpu(buffer, smp_processor_id())

static int trace_hw_branches_enabled __read_mostly;
static int trace_hw_branches_suspended __read_mostly;
static struct trace_array *hw_branch_trace __read_mostly;

-/*
- * Initialize the tracer for the current cpu.
- * The argument is ignored.
- *
- * pre: bts_tracer_lock must be locked.
- */
-static void bts_trace_init_cpu(void *arg)
+static void bts_trace_init_cpu(int cpu)
{
- if (this_tracer)
- ds_release_bts(this_tracer);
+ per_cpu(tracer, cpu) =
+ ds_request_bts_cpu(cpu, per_cpu(buffer, cpu), BTS_BUFFER_SIZE,
+ NULL, (size_t)-1, BTS_KERNEL);

- this_tracer = ds_request_bts(NULL, this_buffer, BTS_BUFFER_SIZE,
- NULL, (size_t)-1, BTS_KERNEL);
- if (IS_ERR(this_tracer)) {
- this_tracer = NULL;
- return;
- }
+ if (IS_ERR(per_cpu(tracer, cpu)))
+ per_cpu(tracer, cpu) = NULL;
}

static int bts_trace_init(struct trace_array *tr)
{
- int cpu, avail;
-
- spin_lock(&bts_tracer_lock);
+ int cpu;

hw_branch_trace = tr;
+ trace_hw_branches_enabled = 0;

- on_each_cpu(bts_trace_init_cpu, NULL, 1);
-
- /* Check on how many cpus we could enable tracing */
- avail = 0;
- for_each_online_cpu(cpu)
- if (per_cpu(tracer, cpu))
- avail++;
+ get_online_cpus();
+ for_each_online_cpu(cpu) {
+ bts_trace_init_cpu(cpu);

- trace_hw_branches_enabled = (avail ? 1 : 0);
+ if (likely(per_cpu(tracer, cpu)))
+ trace_hw_branches_enabled = 1;
+ }
trace_hw_branches_suspended = 0;
-
- spin_unlock(&bts_tracer_lock);
-
+ put_online_cpus();

/* If we could not enable tracing on a single cpu, we fail. */
- return avail ? 0 : -EOPNOTSUPP;
-}
-
-/*
- * Release the tracer for the current cpu.
- * The argument is ignored.
- *
- * pre: bts_tracer_lock must be locked.
- */
-static void bts_trace_release_cpu(void *arg)
-{
- if (this_tracer) {
- ds_release_bts(this_tracer);
- this_tracer = NULL;
- }
+ return trace_hw_branches_enabled ? 0 : -EOPNOTSUPP;
}

static void bts_trace_reset(struct trace_array *tr)
{
- spin_lock(&bts_tracer_lock);
+ int cpu;

- on_each_cpu(bts_trace_release_cpu, NULL, 1);
+ get_online_cpus();
+ for_each_online_cpu(cpu) {
+ if (likely(per_cpu(tracer, cpu))) {
+ ds_release_bts(per_cpu(tracer, cpu));
+ per_cpu(tracer, cpu) = NULL;
+ }
+ }
trace_hw_branches_enabled = 0;
trace_hw_branches_suspended = 0;
-
- spin_unlock(&bts_tracer_lock);
-}
-
-/*
- * Resume tracing on the current cpu.
- * The argument is ignored.
- *
- * pre: bts_tracer_lock must be locked.
- */
-static void bts_trace_resume_cpu(void *arg)
-{
- if (this_tracer)
- ds_resume_bts(this_tracer);
+ put_online_cpus();
}

static void bts_trace_start(struct trace_array *tr)
{
- spin_lock(&bts_tracer_lock);
+ int cpu;

- on_each_cpu(bts_trace_resume_cpu, NULL, 1);
+ get_online_cpus();
+ for_each_online_cpu(cpu)
+ if (likely(per_cpu(tracer, cpu)))
+ ds_resume_bts(per_cpu(tracer, cpu));
trace_hw_branches_suspended = 0;
-
- spin_unlock(&bts_tracer_lock);
-}
-
-/*
- * Suspend tracing on the current cpu.
- * The argument is ignored.
- *
- * pre: bts_tracer_lock must be locked.
- */
-static void bts_trace_suspend_cpu(void *arg)
-{
- if (this_tracer)
- ds_suspend_bts(this_tracer);
+ put_online_cpus();
}

static void bts_trace_stop(struct trace_array *tr)
{
- spin_lock(&bts_tracer_lock);
+ int cpu;

- on_each_cpu(bts_trace_suspend_cpu, NULL, 1);
+ get_online_cpus();
+ for_each_online_cpu(cpu)
+ if (likely(per_cpu(tracer, cpu)))
+ ds_suspend_bts(per_cpu(tracer, cpu));
trace_hw_branches_suspended = 1;
-
- spin_unlock(&bts_tracer_lock);
+ put_online_cpus();
}

static int __cpuinit bts_hotcpu_handler(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
- unsigned int cpu = (unsigned long)hcpu;
-
- spin_lock(&bts_tracer_lock);
-
- if (!trace_hw_branches_enabled)
- goto out;
+ int cpu = (long)hcpu;

switch (action) {
case CPU_ONLINE:
case CPU_DOWN_FAILED:
- smp_call_function_single(cpu, bts_trace_init_cpu, NULL, 1);
-
- if (trace_hw_branches_suspended)
- smp_call_function_single(cpu, bts_trace_suspend_cpu,
- NULL, 1);
+ /* The notification is sent with interrupts enabled. */
+ if (trace_hw_branches_enabled) {
+ bts_trace_init_cpu(cpu);
+
+ if (trace_hw_branches_suspended &&
+ likely(per_cpu(tracer, cpu)))
+ ds_suspend_bts(per_cpu(tracer, cpu));
+ }
break;
+
case CPU_DOWN_PREPARE:
- smp_call_function_single(cpu, bts_trace_release_cpu, NULL, 1);
- break;
+ /* The notification is sent with interrupts enabled. */
+ if (likely(per_cpu(tracer, cpu))) {
+ ds_release_bts(per_cpu(tracer, cpu));
+ per_cpu(tracer, cpu) = NULL;
+ }
}

- out:
- spin_unlock(&bts_tracer_lock);
return NOTIFY_DONE;
}

@@ -274,7 +218,7 @@ static void trace_bts_at(const struct bt
/*
* Collect the trace on the current cpu and write it into the ftrace buffer.
*
- * pre: bts_tracer_lock must be locked
+ * pre: tracing must be suspended on the current cpu
*/
static void trace_bts_cpu(void *arg)
{
@@ -291,10 +235,9 @@ static void trace_bts_cpu(void *arg)
if (unlikely(!this_tracer))
return;

- ds_suspend_bts(this_tracer);
trace = ds_read_bts(this_tracer);
if (!trace)
- goto out;
+ return;

for (at = trace->ds.top; (void *)at < trace->ds.end;
at += trace->ds.size)
@@ -303,18 +246,27 @@ static void trace_bts_cpu(void *arg)
for (at = trace->ds.begin; (void *)at < trace->ds.top;
at += trace->ds.size)
trace_bts_at(trace, at);
-
-out:
- ds_resume_bts(this_tracer);
}

static void trace_bts_prepare(struct trace_iterator *iter)
{
- spin_lock(&bts_tracer_lock);
+ int cpu;

+ get_online_cpus();
+ for_each_online_cpu(cpu)
+ if (likely(per_cpu(tracer, cpu)))
+ ds_suspend_bts(per_cpu(tracer, cpu));
+ /*
+ * We need to collect the trace on the respective cpu since ftrace
+ * implicitly adds the record for the current cpu.
+ * Once that is more flexible, we could collect the data from any cpu.
+ */
on_each_cpu(trace_bts_cpu, iter->tr, 1);

- spin_unlock(&bts_tracer_lock);
+ for_each_online_cpu(cpu)
+ if (likely(per_cpu(tracer, cpu)))
+ ds_resume_bts(per_cpu(tracer, cpu));
+ put_online_cpus();
}

static void trace_bts_close(struct trace_iterator *iter)
@@ -324,12 +276,11 @@ static void trace_bts_close(struct trace

void trace_hw_branch_oops(void)
{
- spin_lock(&bts_tracer_lock);
-
- if (trace_hw_branches_enabled)
+ if (this_tracer) {
+ ds_suspend_bts_noirq(this_tracer);
trace_bts_cpu(hw_branch_trace);
-
- spin_unlock(&bts_tracer_lock);
+ ds_resume_bts_noirq(this_tracer);
+ }
}

struct tracer bts_tracer __read_mostly =
Index: b/arch/x86/kernel/ptrace.c
===================================================================
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -798,8 +798,9 @@ static int ptrace_bts_config(struct task
if (cfg.flags & PTRACE_BTS_O_SCHED)
flags |= BTS_TIMESTAMPS;

- context->tracer = ds_request_bts(child, context->buffer, context->size,
- NULL, (size_t)-1, flags);
+ context->tracer =
+ ds_request_bts_task(child, context->buffer, context->size,
+ NULL, (size_t)-1, flags);
if (unlikely(IS_ERR(context->tracer))) {
int error = PTR_ERR(context->tracer);

Index: b/arch/x86/kernel/ds_selftest.c
===================================================================
--- a/arch/x86/kernel/ds_selftest.c
+++ b/arch/x86/kernel/ds_selftest.c
@@ -10,11 +10,12 @@

#include <linux/kernel.h>
#include <linux/string.h>
+#include <linux/smp.h>

#include <asm/ds.h>

-#define DS_SELFTEST_BUFFER_SIZE 1021 /* Intentionally chose an odd size. */
+#define BUFFER_SIZE 1021 /* Intentionally chose an odd size. */

static int ds_selftest_bts_consistency(const struct bts_trace *trace)
@@ -125,12 +126,12 @@ int ds_selftest_bts(void)
struct bts_tracer *tracer;
int error = 0;
void *top;
- unsigned char buffer[DS_SELFTEST_BUFFER_SIZE];
+ unsigned char buffer[BUFFER_SIZE];

printk(KERN_INFO "[ds] bts selftest...");

- tracer = ds_request_bts(NULL, buffer, DS_SELFTEST_BUFFER_SIZE,
- NULL, (size_t)-1, BTS_KERNEL);
+ tracer = ds_request_bts_cpu(smp_processor_id(), buffer, BUFFER_SIZE,
+ NULL, (size_t)-1, BTS_KERNEL);
if (IS_ERR(tracer)) {
error = PTR_ERR(tracer);
tracer = NULL;