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tracing: Make tracepoint_printk a static_key

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Currently, when tracepoint_printk is set (enabled by the "tp_printk" kernel
command line), it causes trace events to print via printk(). This is a very
dangerous operation, but is useful for debugging.

The issue is, it's seldom used, but it is always checked even if it's not
enabled by the kernel command line. Instead of having this feature called by
a branch against a variable, turn that variable into a static key, and this
will remove the test and jump.

To simplify things, the functions output_printk() and
trace_event_buffer_commit() were moved from trace_events.c to trace.c.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Red Hat) 2016-11-23 15:52:45 -05:00 • committed by Steven Rostedt
parent 929ddbf3ef
commit 4239174570
4 changed files with 83 additions and 41 deletions
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4
include/linux/ftrace.h
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@ -945,6 +945,10 @@ extern int __disable_trace_on_warning;
#define INIT_TRACE_RECURSION .trace_recursion = 0,
#endif
int tracepoint_printk_sysctl(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos);
#else /* CONFIG_TRACING */
static inline void disable_trace_on_warning(void) { }
#endif /* CONFIG_TRACING */