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Commit 80370cb7 authored by Steven Rostedt's avatar Steven Rostedt
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tracing: use raw spinlocks for trace_vprintk 



Impact: prevent locking up by lockdep tracer

The lockdep tracer uses trace_vprintk and thus trace_vprintk can not
call back into lockdep without locking up.

Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
parent ef18012b

kernel/trace/trace.c

+7 −3
Original line number Original line Diff line number Diff line
@@ -1176,7 +1176,8 @@ void trace_graph_return(struct ftrace_graph_ret *trace) 
 */

 */

int trace_vprintk(unsigned long ip, int depth, const char *fmt, va_list args)

int trace_vprintk(unsigned long ip, int depth, const char *fmt, va_list args)

{

{

	static DEFINE_SPINLOCK(trace_buf_lock);

	static raw_spinlock_t trace_buf_lock =

		(raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;

	static u32 trace_buf[TRACE_BUF_SIZE];

	static u32 trace_buf[TRACE_BUF_SIZE];





	struct ring_buffer_event *event;

	struct ring_buffer_event *event;
@@ -1201,7 +1202,9 @@ int trace_vprintk(unsigned long ip, int depth, const char *fmt, va_list args) 
	if (unlikely(atomic_read(&data->disabled)))

	if (unlikely(atomic_read(&data->disabled)))

		goto out;

		goto out;





	spin_lock_irqsave(&trace_buf_lock, flags);

	/* Lockdep uses trace_printk for lock tracing */

	local_irq_save(flags);

	__raw_spin_lock(&trace_buf_lock);

	len = vbin_printf(trace_buf, TRACE_BUF_SIZE, fmt, args);

	len = vbin_printf(trace_buf, TRACE_BUF_SIZE, fmt, args);





	if (len > TRACE_BUF_SIZE || len < 0)

	if (len > TRACE_BUF_SIZE || len < 0)
@@ -1220,7 +1223,8 @@ int trace_vprintk(unsigned long ip, int depth, const char *fmt, va_list args) 
	ring_buffer_unlock_commit(tr->buffer, event);

	ring_buffer_unlock_commit(tr->buffer, event);





out_unlock:

out_unlock:

	spin_unlock_irqrestore(&trace_buf_lock, flags);

	__raw_spin_unlock(&trace_buf_lock);

	local_irq_restore(flags);





out:

out:

	ftrace_preempt_enable(resched);

	ftrace_preempt_enable(resched);