tracing: Use the perf recursion protection from trace event

When we commit a trace to perf, we first check if we are
recursing in the same buffer so that we don't mess-up the buffer
with a recursing trace. But later on, we do the same check from
perf to avoid commit recursion. The recursion check is desired
early before we touch the buffer but we want to do this check
only once.

Then export the recursion protection from perf and use it from
the trace events before submitting a trace.

v2: Put appropriate Reported-by tag

Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Jason Baron <jbaron@redhat.com>
LKML-Reference: <1258864015-10579-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 17 insertions, 30 deletions

diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 51213b0..0bb9348 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -477,10 +477,11 @@ static int sys_prof_refcount_exit;
 static void prof_syscall_enter(struct pt_regs *regs, long id)
 {
 	struct syscall_metadata *sys_data;
-	struct perf_trace_buf *trace_buf;
 	struct syscall_trace_enter *rec;
 	unsigned long flags;
+	char *trace_buf;
 	char *raw_data;
+	int *recursion;
 	int syscall_nr;
 	int size;
 	int cpu;
@@ -505,6 +506,9 @@ static void prof_syscall_enter(struct pt_regs *regs, long id)
 	/* Protect the per cpu buffer, begin the rcu read side */
 	local_irq_save(flags);
 
+	if (perf_swevent_get_recursion_context(&recursion))
+		goto end_recursion;
+
 	cpu = smp_processor_id();
 
 	if (in_nmi())
@@ -515,18 +519,7 @@ static void prof_syscall_enter(struct pt_regs *regs, long id)
 	if (!trace_buf)
 		goto end;
 
-	trace_buf = per_cpu_ptr(trace_buf, cpu);
-
-	if (trace_buf->recursion++)
-		goto end_recursion;
-
-	/*
-	 * Make recursion update visible before entering perf_tp_event
-	 * so that we protect from perf recursions.
-	 */
-	barrier();
-
-	raw_data = trace_buf->buf;
+	raw_data = per_cpu_ptr(trace_buf, cpu);
 
 	/* zero the dead bytes from align to not leak stack to user */
 	*(u64 *)(&raw_data[size - sizeof(u64)]) = 0ULL;
@@ -539,9 +532,9 @@ static void prof_syscall_enter(struct pt_regs *regs, long id)
 			       (unsigned long *)&rec->args);
 	perf_tp_event(sys_data->enter_id, 0, 1, rec, size);
 
-end_recursion:
-	trace_buf->recursion--;
 end:
+	perf_swevent_put_recursion_context(recursion);
+end_recursion:
 	local_irq_restore(flags);
 }
 
@@ -588,10 +581,11 @@ static void prof_syscall_exit(struct pt_regs *regs, long ret)
 {
 	struct syscall_metadata *sys_data;
 	struct syscall_trace_exit *rec;
-	struct perf_trace_buf *trace_buf;
 	unsigned long flags;
 	int syscall_nr;
+	char *trace_buf;
 	char *raw_data;
+	int *recursion;
 	int size;
 	int cpu;
 
@@ -617,6 +611,10 @@ static void prof_syscall_exit(struct pt_regs *regs, long ret)
 
 	/* Protect the per cpu buffer, begin the rcu read side */
 	local_irq_save(flags);
+
+	if (perf_swevent_get_recursion_context(&recursion))
+		goto end_recursion;
+
 	cpu = smp_processor_id();
 
 	if (in_nmi())
@@ -627,18 +625,7 @@ static void prof_syscall_exit(struct pt_regs *regs, long ret)
 	if (!trace_buf)
 		goto end;
 
-	trace_buf = per_cpu_ptr(trace_buf, cpu);
-
-	if (trace_buf->recursion++)
-		goto end_recursion;
-
-	/*
-	 * Make recursion update visible before entering perf_tp_event
-	 * so that we protect from perf recursions.
-	 */
-	barrier();
-
-	raw_data = trace_buf->buf;
+	raw_data = per_cpu_ptr(trace_buf, cpu);
 
 	/* zero the dead bytes from align to not leak stack to user */
 	*(u64 *)(&raw_data[size - sizeof(u64)]) = 0ULL;
@@ -652,9 +639,9 @@ static void prof_syscall_exit(struct pt_regs *regs, long ret)
 
 	perf_tp_event(sys_data->exit_id, 0, 1, rec, size);
 
-end_recursion:
-	trace_buf->recursion--;
 end:
+	perf_swevent_put_recursion_context(recursion);
+end_recursion:
 	local_irq_restore(flags);
 }