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Commit 4a2b4b22 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: Introduce preempt_count accessor functions 



Replace the single preempt_count() 'function' that's an lvalue with
two proper functions:

 preempt_count() - returns the preempt_count value as rvalue
 preempt_count_set() - Allows setting the preempt-count value

Also provide preempt_count_ptr() as a convenience wrapper to implement
all modifying operations.

Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-orxrbycjozopqfhb4dxdkdvb@git.kernel.org


[ Fixed build failure. ]
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent ea811747

include/linux/preempt.h

+19 −6
Original line number Diff line number Diff line
@@ -10,19 +10,32 @@ 
#include <linux/linkage.h>

#include <linux/list.h>



static __always_inline int preempt_count(void)

{

	return current_thread_info()->preempt_count;

}



static __always_inline int *preempt_count_ptr(void)

{

	return &current_thread_info()->preempt_count;

}



static __always_inline void preempt_count_set(int pc)

{

	*preempt_count_ptr() = pc;

}



#if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER)

  extern void add_preempt_count(int val);

  extern void sub_preempt_count(int val);

#else

# define add_preempt_count(val)	do { preempt_count() += (val); } while (0)

# define sub_preempt_count(val)	do { preempt_count() -= (val); } while (0)

# define add_preempt_count(val)	do { *preempt_count_ptr() += (val); } while (0)

# define sub_preempt_count(val)	do { *preempt_count_ptr() -= (val); } while (0)

#endif



#define inc_preempt_count() add_preempt_count(1)

#define dec_preempt_count() sub_preempt_count(1)



#define preempt_count()	(current_thread_info()->preempt_count)



#ifdef CONFIG_PREEMPT



asmlinkage void preempt_schedule(void);
@@ -81,9 +94,9 @@ do { \ 


/* For debugging and tracer internals only! */

#define add_preempt_count_notrace(val)			\

	do { preempt_count() += (val); } while (0)

	do { *preempt_count_ptr() += (val); } while (0)

#define sub_preempt_count_notrace(val)			\

	do { preempt_count() -= (val); } while (0)

	do { *preempt_count_ptr() -= (val); } while (0)

#define inc_preempt_count_notrace() add_preempt_count_notrace(1)

#define dec_preempt_count_notrace() sub_preempt_count_notrace(1)

init/main.c

+1 −1
Original line number Diff line number Diff line
@@ -692,7 +692,7 @@ int __init_or_module do_one_initcall(initcall_t fn) 


	if (preempt_count() != count) {

		sprintf(msgbuf, "preemption imbalance ");

		preempt_count() = count;

		preempt_count_set(count);

	}

	if (irqs_disabled()) {

		strlcat(msgbuf, "disabled interrupts ", sizeof(msgbuf));

kernel/sched/core.c

+2 −2
Original line number Diff line number Diff line
@@ -2219,7 +2219,7 @@ void __kprobes add_preempt_count(int val) 
	if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))

		return;

#endif

	preempt_count() += val;

	add_preempt_count_notrace(val);

#ifdef CONFIG_DEBUG_PREEMPT

	/*

	 * Spinlock count overflowing soon?
@@ -2250,7 +2250,7 @@ void __kprobes sub_preempt_count(int val) 


	if (preempt_count() == val)

		trace_preempt_on(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));

	preempt_count() -= val;

	sub_preempt_count_notrace(val);

}

EXPORT_SYMBOL(sub_preempt_count);

kernel/softirq.c

+2 −2
Original line number Diff line number Diff line
@@ -106,7 +106,7 @@ static void __local_bh_disable(unsigned long ip, unsigned int cnt) 
	 * We must manually increment preempt_count here and manually

	 * call the trace_preempt_off later.

	 */

	preempt_count() += cnt;

	add_preempt_count_notrace(cnt);

	/*

	 * Were softirqs turned off above:

	 */
@@ -256,7 +256,7 @@ asmlinkage void __do_softirq(void) 
				       " exited with %08x?\n", vec_nr,

				       softirq_to_name[vec_nr], h->action,

				       prev_count, preempt_count());

				preempt_count() = prev_count;

				preempt_count_set(prev_count);

			}



			rcu_bh_qs(cpu);

kernel/timer.c

+4 −4
Original line number Diff line number Diff line
@@ -1092,7 +1092,7 @@ static int cascade(struct tvec_base *base, struct tvec *tv, int index) 
static void call_timer_fn(struct timer_list *timer, void (*fn)(unsigned long),

			  unsigned long data)

{

	int preempt_count = preempt_count();

	int count = preempt_count();



#ifdef CONFIG_LOCKDEP

	/*
@@ -1119,16 +1119,16 @@ static void call_timer_fn(struct timer_list *timer, void (*fn)(unsigned long), 


	lock_map_release(&lockdep_map);



	if (preempt_count != preempt_count()) {

	if (count != preempt_count()) {

		WARN_ONCE(1, "timer: %pF preempt leak: %08x -> %08x\n",

			  fn, preempt_count, preempt_count());

			  fn, count, preempt_count());

		/*

		 * Restore the preempt count. That gives us a decent

		 * chance to survive and extract information. If the

		 * callback kept a lock held, bad luck, but not worse

		 * than the BUG() we had.

		 */

		preempt_count() = preempt_count;

		preempt_count_set(count);

	}

}