Commit 5c4853b6 authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Ingo Molnar
Browse files

lockdep: Simplify a bit hardirq <-> softirq transitions 



Instead of saving the hardirq state on a per CPU variable, which require
an explicit call before the softirq handling and some complication,
just save and restore the hardirq tracing state through functions
return values and parameters.

It simplifies a bit the black magic that works around the fact that
softirqs can be called from hardirqs while hardirqs can nest on softirqs
but those two cases have very different semantics and only the latter
case assume both states.

Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1384906054-30676-1-git-send-email-fweisbec@gmail.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 7d5b1583

kernel/softirq.c

+16 −21
Original line number Diff line number Diff line
@@ -213,40 +213,35 @@ EXPORT_SYMBOL(local_bh_enable_ip); 


#ifdef CONFIG_TRACE_IRQFLAGS

/*

 * Convoluted means of passing __do_softirq() a message through the various

 * architecture execute_on_stack() bits.

 *

 * When we run softirqs from irq_exit() and thus on the hardirq stack we need

 * to keep the lockdep irq context tracking as tight as possible in order to

 * not miss-qualify lock contexts and miss possible deadlocks.

 */

static DEFINE_PER_CPU(int, softirq_from_hardirq);



static inline void lockdep_softirq_from_hardirq(void)

static inline bool lockdep_softirq_start(void)

{

	this_cpu_write(softirq_from_hardirq, 1);

}

	bool in_hardirq = false;



static inline void lockdep_softirq_start(void)

{

	if (this_cpu_read(softirq_from_hardirq))

	if (trace_hardirq_context(current)) {

		in_hardirq = true;

		trace_hardirq_exit();

	}



	lockdep_softirq_enter();



	return in_hardirq;

}



static inline void lockdep_softirq_end(void)

static inline void lockdep_softirq_end(bool in_hardirq)

{

	lockdep_softirq_exit();

	if (this_cpu_read(softirq_from_hardirq)) {

		this_cpu_write(softirq_from_hardirq, 0);



	if (in_hardirq)

		trace_hardirq_enter();

}

}



#else

static inline void lockdep_softirq_from_hardirq(void) { }

static inline void lockdep_softirq_start(void) { }

static inline void lockdep_softirq_end(void) { }

static inline bool lockdep_softirq_start(void) { return false; }

static inline void lockdep_softirq_end(bool in_hardirq) { }

#endif



asmlinkage void __do_softirq(void)
@@ -255,6 +250,7 @@ asmlinkage void __do_softirq(void) 
	unsigned long old_flags = current->flags;

	int max_restart = MAX_SOFTIRQ_RESTART;

	struct softirq_action *h;

	bool in_hardirq;

	__u32 pending;

	int cpu;
@@ -269,7 +265,7 @@ asmlinkage void __do_softirq(void) 
	account_irq_enter_time(current);



	__local_bh_disable(_RET_IP_, SOFTIRQ_OFFSET);

	lockdep_softirq_start();

	in_hardirq = lockdep_softirq_start();



	cpu = smp_processor_id();

restart:
@@ -316,7 +312,7 @@ restart: 
		wakeup_softirqd();

	}



	lockdep_softirq_end();

	lockdep_softirq_end(in_hardirq);

	account_irq_exit_time(current);

	__local_bh_enable(SOFTIRQ_OFFSET);

	WARN_ON_ONCE(in_interrupt());
@@ -365,7 +361,6 @@ void irq_enter(void) 
static inline void invoke_softirq(void)

{

	if (!force_irqthreads) {

		lockdep_softirq_from_hardirq();

#ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK

		/*

		 * We can safely execute softirq on the current stack if

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