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/kernel/trace/trace_hw_branches.c b/kernel/trace/trace_hw_branches.c
index 8b2109a..50565d8 100644
--- 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);
+ get_online_cpus();
+ for_each_online_cpu(cpu) {
+ bts_trace_init_cpu(cpu);
- /* Check on how many cpus we could enable tracing */
- avail = 0;
- for_each_online_cpu(cpu)
- if (per_cpu(tracer, cpu))
- avail++;
-
- 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);
+ /* The notification is sent with interrupts enabled. */
+ if (trace_hw_branches_enabled) {
+ bts_trace_init_cpu(cpu);
- if (trace_hw_branches_suspended)
- smp_call_function_single(cpu, bts_trace_suspend_cpu,
- NULL, 1);
+ 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 @@
/*
* 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 @@
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 @@
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 @@
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 =