ftrace: disable preemption when recursion locked

As the documentation explained, ftrace_test_recursion_trylock()
and ftrace_test_recursion_unlock() were supposed to disable and
enable preemption properly, however currently this work is done
outside of the function, which could be missing by mistake.

And since the internal using of trace_test_and_set_recursion()
and trace_clear_recursion() also require preemption disabled, we
can just merge the logical.

This patch will make sure the preemption has been disabled when
trace_test_and_set_recursion() return bit >= 0, and
trace_clear_recursion() will enable the preemption if previously
enabled.

Link: https://lkml.kernel.org/r/[email protected]

CC: Petr Mladek <[email protected]>
Cc: Guo Ren <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Paul Walmsley <[email protected]>
Cc: Palmer Dabbelt <[email protected]>
Cc: Albert Ou <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Jiri Kosina <[email protected]>
Cc: Joe Lawrence <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Nicholas Piggin <[email protected]>
Cc: Jisheng Zhang <[email protected]>
CC: Steven Rostedt <[email protected]>
CC: Miroslav Benes <[email protected]>
Reported-by: Abaci <[email protected]>
Suggested-by: Peter Zijlstra <[email protected]>
Signed-off-by: Michael Wang <[email protected]>
[ Removed extra line in comment - SDR ]
Signed-off-by: Steven Rostedt (VMware) <[email protected]>

1 files changed, 10 insertions, 1 deletions

diff --git a/include/linux/trace_recursion.h b/include/linux/trace_recursion.h
index 24f284eb55a7..a13f23b04d73 100644
--- a/include/linux/trace_recursion.h
+++ b/include/linux/trace_recursion.h
@@ -155,6 +155,9 @@ extern void ftrace_record_recursion(unsigned long ip, unsigned long parent_ip);
 # define do_ftrace_record_recursion(ip, pip)	do { } while (0)
 #endif
 
+/*
+ * Preemption is promised to be disabled when return bit >= 0.
+ */
 static __always_inline int trace_test_and_set_recursion(unsigned long ip, unsigned long pip,
 							int start, int max)
 {
@@ -189,14 +192,20 @@ static __always_inline int trace_test_and_set_recursion(unsigned long ip, unsign
 	current->trace_recursion = val;
 	barrier();
 
+	preempt_disable_notrace();
+
 	return bit + 1;
 }
 
+/*
+ * Preemption will be enabled (if it was previously enabled).
+ */
 static __always_inline void trace_clear_recursion(int bit)
 {
 	if (!bit)
 		return;
 
+	preempt_enable_notrace();
 	barrier();
 	bit--;
 	trace_recursion_clear(bit);
@@ -209,7 +218,7 @@ static __always_inline void trace_clear_recursion(int bit)
  * tracing recursed in the same context (normal vs interrupt),
  *
  * Returns: -1 if a recursion happened.
- *           >= 0 if no recursion
+ *           >= 0 if no recursion.
  */
 static __always_inline int ftrace_test_recursion_trylock(unsigned long ip,
 							 unsigned long parent_ip)