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Commit 3189cdb3 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt
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tracing: protect trace_printk from recursion 



trace_printk can be called from any context, including NMIs.
If this happens, then we must test for for recursion before
grabbing any spinlocks.

This patch prevents trace_printk from being called recursively.

[ Impact: prevent hard lockup in lockdep event tracer ]

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 261842b7

kernel/trace/trace.c

+8 −2
Original line number Original line Diff line number Diff line
@@ -1259,6 +1259,7 @@ int trace_vbprintk(unsigned long ip, const char *fmt, va_list args) 
	struct trace_array_cpu *data;

	struct trace_array_cpu *data;

	struct bprint_entry *entry;

	struct bprint_entry *entry;

	unsigned long flags;

	unsigned long flags;

	int disable;

	int resched;

	int resched;

	int cpu, len = 0, size, pc;

	int cpu, len = 0, size, pc;
@@ -1273,7 +1274,8 @@ int trace_vbprintk(unsigned long ip, const char *fmt, va_list args) 
	cpu = raw_smp_processor_id();

	cpu = raw_smp_processor_id();

	data = tr->data[cpu];

	data = tr->data[cpu];





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

	disable = atomic_inc_return(&data->disabled);

	if (unlikely(disable != 1))

		goto out;

		goto out;





	/* Lockdep uses trace_printk for lock tracing */

	/* Lockdep uses trace_printk for lock tracing */
@@ -1301,6 +1303,7 @@ int trace_vbprintk(unsigned long ip, const char *fmt, va_list args) 
	local_irq_restore(flags);

	local_irq_restore(flags);





out:

out:

	atomic_dec_return(&data->disabled);

	ftrace_preempt_enable(resched);

	ftrace_preempt_enable(resched);

	unpause_graph_tracing();

	unpause_graph_tracing();
@@ -1320,6 +1323,7 @@ int trace_vprintk(unsigned long ip, const char *fmt, va_list args) 
	int cpu, len = 0, size, pc;

	int cpu, len = 0, size, pc;

	struct print_entry *entry;

	struct print_entry *entry;

	unsigned long irq_flags;

	unsigned long irq_flags;

	int disable;





	if (tracing_disabled || tracing_selftest_running)

	if (tracing_disabled || tracing_selftest_running)

		return 0;

		return 0;
@@ -1329,7 +1333,8 @@ int trace_vprintk(unsigned long ip, const char *fmt, va_list args) 
	cpu = raw_smp_processor_id();

	cpu = raw_smp_processor_id();

	data = tr->data[cpu];

	data = tr->data[cpu];





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

	disable = atomic_inc_return(&data->disabled);

	if (unlikely(disable != 1))

		goto out;

		goto out;





	pause_graph_tracing();

	pause_graph_tracing();
@@ -1357,6 +1362,7 @@ int trace_vprintk(unsigned long ip, const char *fmt, va_list args) 
	raw_local_irq_restore(irq_flags);

	raw_local_irq_restore(irq_flags);

	unpause_graph_tracing();

	unpause_graph_tracing();

 out:

 out:

	atomic_dec_return(&data->disabled);

	preempt_enable_notrace();

	preempt_enable_notrace();





	return len;

	return len;