x86, bts, hw-branch-tracer: add _noirq variants to the debug store interface
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>
Cc: roland@redhat.com
Cc: eranian@googlemail.com
Cc: oleg@redhat.com
Cc: juan.villacis@intel.com
Cc: ak@linux.jf.intel.com
LKML-Reference: <20090403144555.658136000@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/ds.c b/arch/x86/kernel/ds.c
index 2071b99..21a3852 100644
--- a/arch/x86/kernel/ds.c
+++ b/arch/x86/kernel/ds.c
@@ -245,60 +245,50 @@
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;
+
+ /* The traced cpu; only valid if task is NULL: */
+ int cpu;
};
-static DEFINE_PER_CPU(struct ds_context *, system_context_array);
-
-#define system_context per_cpu(system_context_array, smp_processor_id())
+static DEFINE_PER_CPU(struct ds_context *, cpu_context);
-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);
@@ -306,7 +296,7 @@
return context;
}
-static inline void ds_put_context(struct ds_context *context)
+static void ds_put_context(struct ds_context *context)
{
struct task_struct *task;
unsigned long irq;
@@ -328,8 +318,15 @@
if (task)
clear_tsk_thread_flag(task, TIF_DS_AREA_MSR);
- if (!task || (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);
@@ -340,6 +337,31 @@
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.
@@ -622,6 +644,7 @@
* 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;
@@ -630,7 +653,7 @@
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;
@@ -643,7 +666,7 @@
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;
@@ -660,25 +683,27 @@
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. */
@@ -690,42 +715,46 @@
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);
@@ -735,13 +764,27 @@
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. */
@@ -753,37 +796,43 @@
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);
@@ -793,17 +842,27 @@
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)
+{
+ return ds_request_pebs(task, 0, base, size, ovfl, th, flags);
+}
+
+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);
+}
+
+static void ds_free_bts(struct bts_tracer *tracer)
{
struct task_struct *task;
- if (!tracer)
- return;
-
task = tracer->ds.context->task;
- ds_suspend_bts(tracer);
-
WARN_ON_ONCE(tracer->ds.context->bts_master != tracer);
tracer->ds.context->bts_master = NULL;
@@ -817,9 +876,69 @@
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;
@@ -827,29 +946,60 @@
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))
@@ -857,25 +1007,77 @@
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;
- task = tracer->ds.context->task;
+ tracer->flags = tracer->trace.ds.flags;
- ds_suspend_pebs(tracer);
+ task = tracer->ds.context->task;
+ cpu = tracer->ds.context->cpu;
+
+ 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;
@@ -886,16 +1088,68 @@
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)
@@ -1004,26 +1258,6 @@
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",
@@ -1127,3 +1361,29 @@
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);
diff --git a/arch/x86/kernel/ds_selftest.c b/arch/x86/kernel/ds_selftest.c
index 8c46fbf..e5a263c 100644
--- 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 @@
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;
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 7c21d1e..adbb243 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -800,8 +800,9 @@
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);