ftrace: add necessary locking for ftrace records
The new design of pre-recorded mcounts and updating the code outside of
kstop_machine has changed the way the records themselves are protected.
This patch uses the ftrace_lock to protect the records. Note, the lock
still does not need to be taken within calls that are only called via
kstop_machine, since the that code can not run while the spin lock is held.
Also removed the hash_lock needed for the daemon when MCOUNT_RECORD is
configured. Also did a slight cleanup of an unused variable.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 11d94f2..43665ad 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -81,7 +81,7 @@
static int __register_ftrace_function(struct ftrace_ops *ops)
{
- /* Should never be called by interrupts */
+ /* should not be called from interrupt context */
spin_lock(&ftrace_lock);
ops->next = ftrace_list;
@@ -115,6 +115,7 @@
struct ftrace_ops **p;
int ret = 0;
+ /* should not be called from interrupt context */
spin_lock(&ftrace_lock);
/*
@@ -153,6 +154,21 @@
#ifdef CONFIG_DYNAMIC_FTRACE
+#ifndef CONFIG_FTRACE_MCOUNT_RECORD
+/*
+ * The hash lock is only needed when the recording of the mcount
+ * callers are dynamic. That is, by the caller themselves and
+ * not recorded via the compilation.
+ */
+static DEFINE_SPINLOCK(ftrace_hash_lock);
+#define ftrace_hash_lock(flags) spin_lock_irqsave(ftrace_hash_lock, flags)
+#define ftrace_hash_unlock(flags) spin_lock_irqsave(ftrace_hash_lock, flags)
+#else
+/* This is protected via the ftrace_lock with MCOUNT_RECORD. */
+#define ftrace_hash_lock(flags) do { (void)flags; } while (0)
+#define ftrace_hash_unlock(flags) do { } while(0)
+#endif
+
static struct task_struct *ftraced_task;
enum {
@@ -171,7 +187,6 @@
static DEFINE_PER_CPU(int, ftrace_shutdown_disable_cpu);
-static DEFINE_SPINLOCK(ftrace_shutdown_lock);
static DEFINE_MUTEX(ftraced_lock);
static DEFINE_MUTEX(ftrace_regex_lock);
@@ -310,7 +325,7 @@
if (ftrace_disabled || !start)
return;
- /* No interrupt should call this */
+ /* should not be called from interrupt context */
spin_lock(&ftrace_lock);
for (pg = ftrace_pages_start; pg; pg = pg->next) {
@@ -362,7 +377,6 @@
unsigned long flags;
unsigned long key;
int resched;
- int atomic;
int cpu;
if (!ftrace_enabled || ftrace_disabled)
@@ -392,9 +406,7 @@
if (ftrace_ip_in_hash(ip, key))
goto out;
- atomic = irqs_disabled();
-
- spin_lock_irqsave(&ftrace_shutdown_lock, flags);
+ ftrace_hash_lock(flags);
/* This ip may have hit the hash before the lock */
if (ftrace_ip_in_hash(ip, key))
@@ -411,7 +423,7 @@
ftraced_trigger = 1;
out_unlock:
- spin_unlock_irqrestore(&ftrace_shutdown_lock, flags);
+ ftrace_hash_unlock(flags);
out:
per_cpu(ftrace_shutdown_disable_cpu, cpu)--;
@@ -887,6 +899,8 @@
(*pos)++;
+ /* should not be called from interrupt context */
+ spin_lock(&ftrace_lock);
retry:
if (iter->idx >= iter->pg->index) {
if (iter->pg->next) {
@@ -910,6 +924,7 @@
goto retry;
}
}
+ spin_unlock(&ftrace_lock);
iter->pos = *pos;
@@ -1023,8 +1038,8 @@
unsigned long type = enable ? FTRACE_FL_FILTER : FTRACE_FL_NOTRACE;
unsigned i;
- /* keep kstop machine from running */
- preempt_disable();
+ /* should not be called from interrupt context */
+ spin_lock(&ftrace_lock);
if (enable)
ftrace_filtered = 0;
pg = ftrace_pages_start;
@@ -1037,7 +1052,7 @@
}
pg = pg->next;
}
- preempt_enable();
+ spin_unlock(&ftrace_lock);
}
static int
@@ -1149,8 +1164,8 @@
}
}
- /* keep kstop machine from running */
- preempt_disable();
+ /* should not be called from interrupt context */
+ spin_lock(&ftrace_lock);
if (enable)
ftrace_filtered = 1;
pg = ftrace_pages_start;
@@ -1187,7 +1202,7 @@
}
pg = pg->next;
}
- preempt_enable();
+ spin_unlock(&ftrace_lock);
}
static ssize_t
@@ -1551,6 +1566,7 @@
p = start;
while (p < end) {
addr = ftrace_call_adjust(*p++);
+ /* should not be called from interrupt context */
spin_lock(&ftrace_lock);
ftrace_record_ip(addr);
spin_unlock(&ftrace_lock);