Commit fddf9055 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

lockdep: Use raw_cpu_*() for per-cpu variables 



Sven reported that commit a21ee605 ("lockdep: Change
hardirq{s_enabled,_context} to per-cpu variables") caused trouble on
s390 because their this_cpu_*() primitives disable preemption which
then lands back tracing.

On the one hand, per-cpu ops should use preempt_*able_notrace() and
raw_local_irq_*(), on the other hand, we can trivialy use raw_cpu_*()
ops for this.

Fixes: a21ee605 ("lockdep: Change hardirq{s_enabled,_context} to per-cpu variables")
Reported-by: default avatarSven Schnelle <svens@linux.ibm.com>
Reviewed-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: default avatarMarco Elver <elver@google.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200821085348.192346882@infradead.org
parent d012a719

include/linux/irqflags.h

+3 −3
Original line number Diff line number Diff line
@@ -53,13 +53,13 @@ DECLARE_PER_CPU(int, hardirq_context); 
  extern void trace_hardirqs_off_finish(void);

  extern void trace_hardirqs_on(void);

  extern void trace_hardirqs_off(void);

# define lockdep_hardirq_context()	(this_cpu_read(hardirq_context))

# define lockdep_hardirq_context()	(raw_cpu_read(hardirq_context))

# define lockdep_softirq_context(p)	((p)->softirq_context)

# define lockdep_hardirqs_enabled()	(this_cpu_read(hardirqs_enabled))

# define lockdep_softirqs_enabled(p)	((p)->softirqs_enabled)

# define lockdep_hardirq_enter()			\

do {							\

	if (this_cpu_inc_return(hardirq_context) == 1)	\

	if (__this_cpu_inc_return(hardirq_context) == 1)\

		current->hardirq_threaded = 0;		\

} while (0)

# define lockdep_hardirq_threaded()		\
@@ -68,7 +68,7 @@ do { \ 
} while (0)

# define lockdep_hardirq_exit()			\

do {						\

	this_cpu_dec(hardirq_context);		\

	__this_cpu_dec(hardirq_context);	\

} while (0)

# define lockdep_softirq_enter()		\

do {						\

include/linux/lockdep.h

+13 −5
Original line number Diff line number Diff line
@@ -535,19 +535,27 @@ do { \ 
DECLARE_PER_CPU(int, hardirqs_enabled);

DECLARE_PER_CPU(int, hardirq_context);



/*

 * The below lockdep_assert_*() macros use raw_cpu_read() to access the above

 * per-cpu variables. This is required because this_cpu_read() will potentially

 * call into preempt/irq-disable and that obviously isn't right. This is also

 * correct because when IRQs are enabled, it doesn't matter if we accidentally

 * read the value from our previous CPU.

 */



#define lockdep_assert_irqs_enabled()					\

do {									\

	WARN_ON_ONCE(debug_locks && !this_cpu_read(hardirqs_enabled));	\

	WARN_ON_ONCE(debug_locks && !raw_cpu_read(hardirqs_enabled));	\

} while (0)



#define lockdep_assert_irqs_disabled()					\

do {									\

	WARN_ON_ONCE(debug_locks && this_cpu_read(hardirqs_enabled));	\

	WARN_ON_ONCE(debug_locks && raw_cpu_read(hardirqs_enabled));	\

} while (0)



#define lockdep_assert_in_irq()						\

do {									\

	WARN_ON_ONCE(debug_locks && !this_cpu_read(hardirq_context));	\

	WARN_ON_ONCE(debug_locks && !raw_cpu_read(hardirq_context));	\

} while (0)



#define lockdep_assert_preemption_enabled()				\
@@ -555,7 +563,7 @@ do { \ 
	WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_COUNT)	&&		\

		     debug_locks			&&		\

		     (preempt_count() != 0		||		\

		      !this_cpu_read(hardirqs_enabled)));		\

		      !raw_cpu_read(hardirqs_enabled)));		\

} while (0)



#define lockdep_assert_preemption_disabled()				\
@@ -563,7 +571,7 @@ do { \ 
	WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_COUNT)	&&		\

		     debug_locks			&&		\

		     (preempt_count() == 0		&&		\

		      this_cpu_read(hardirqs_enabled)));		\

		      raw_cpu_read(hardirqs_enabled)));			\

} while (0)



#else

kernel/locking/lockdep.c

+2 −2
Original line number Diff line number Diff line
@@ -3756,7 +3756,7 @@ void noinstr lockdep_hardirqs_on(unsigned long ip) 


skip_checks:

	/* we'll do an OFF -> ON transition: */

	this_cpu_write(hardirqs_enabled, 1);

	__this_cpu_write(hardirqs_enabled, 1);

	trace->hardirq_enable_ip = ip;

	trace->hardirq_enable_event = ++trace->irq_events;

	debug_atomic_inc(hardirqs_on_events);
@@ -3795,7 +3795,7 @@ void noinstr lockdep_hardirqs_off(unsigned long ip) 
		/*

		 * We have done an ON -> OFF transition:

		 */

		this_cpu_write(hardirqs_enabled, 0);

		__this_cpu_write(hardirqs_enabled, 0);

		trace->hardirq_disable_ip = ip;

		trace->hardirq_disable_event = ++trace->irq_events;

		debug_atomic_inc(hardirqs_off_events);

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