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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: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt 2009-04-17 16:13:55 -04:00 committed by Steven Rostedt
parent 261842b7c9
commit 3189cdb316
1 changed files with 8 additions and 2 deletions
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10
kernel/trace/trace.c
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@ -1259,6 +1259,7 @@ int trace_vbprintk(unsigned long ip, const char *fmt, va_list args)
struct trace_array_cpu *data;
struct bprint_entry *entry;
unsigned long flags;
int disable;
int resched;
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();
data = tr->data[cpu];
if (unlikely(atomic_read(&data->disabled)))
disable = atomic_inc_return(&data->disabled);
if (unlikely(disable != 1))
goto out;
/* Lockdep uses trace_printk for lock tracing */
@ -1301,6 +1303,7 @@ out_unlock:
local_irq_restore(flags);
out:
atomic_dec_return(&data->disabled);
ftrace_preempt_enable(resched);
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;
struct print_entry *entry;
unsigned long irq_flags;
int disable;
if (tracing_disabled || tracing_selftest_running)
return 0;
@ -1329,7 +1333,8 @@ int trace_vprintk(unsigned long ip, const char *fmt, va_list args)
cpu = raw_smp_processor_id();
data = tr->data[cpu];
if (unlikely(atomic_read(&data->disabled)))
disable = atomic_inc_return(&data->disabled);
if (unlikely(disable != 1))
goto out;
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);
unpause_graph_tracing();
out:
atomic_dec_return(&data->disabled);
preempt_enable_notrace();
return len;