Commit 153bedba authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Ingo Molnar
Browse files

irq_work: Convert flags to atomic_t 



We need to convert flags to atomic_t in order to later fix an ordering
issue on atomic_cmpxchg() failure. This will allow us to use atomic_fetch_or().

Also clarify the nature of those flags.

[ mingo: Converted two more usage site the original patch missed. ]

Signed-off-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191108160858.31665-2-frederic@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 31f4f5b4

include/linux/irq_work.h

+7 −3
Original line number Diff line number Diff line
@@ -22,7 +22,7 @@ 
#define IRQ_WORK_CLAIMED	(IRQ_WORK_PENDING | IRQ_WORK_BUSY)



struct irq_work {

	unsigned long flags;

	atomic_t flags;

	struct llist_node llnode;

	void (*func)(struct irq_work *);

};
@@ -30,11 +30,15 @@ struct irq_work { 
static inline

void init_irq_work(struct irq_work *work, void (*func)(struct irq_work *))

{

	work->flags = 0;

	atomic_set(&work->flags, 0);

	work->func = func;

}



#define DEFINE_IRQ_WORK(name, _f) struct irq_work name = { .func = (_f), }

#define DEFINE_IRQ_WORK(name, _f) struct irq_work name = {	\

		.flags = ATOMIC_INIT(0),			\

		.func  = (_f)					\

}





bool irq_work_queue(struct irq_work *work);

bool irq_work_queue_on(struct irq_work *work, int cpu);

kernel/bpf/stackmap.c

+1 −1
Original line number Diff line number Diff line
@@ -289,7 +289,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, 


	if (in_nmi()) {

		work = this_cpu_ptr(&up_read_work);

		if (work->irq_work.flags & IRQ_WORK_BUSY)

		if (atomic_read(&work->irq_work.flags) & IRQ_WORK_BUSY)

			/* cannot queue more up_read, fallback */

			irq_work_busy = true;

	}

kernel/irq_work.c

+9 −9
Original line number Diff line number Diff line
@@ -29,16 +29,16 @@ static DEFINE_PER_CPU(struct llist_head, lazy_list); 
 */

static bool irq_work_claim(struct irq_work *work)

{

	unsigned long flags, oflags, nflags;

	int flags, oflags, nflags;



	/*

	 * Start with our best wish as a premise but only trust any

	 * flag value after cmpxchg() result.

	 */

	flags = work->flags & ~IRQ_WORK_PENDING;

	flags = atomic_read(&work->flags) & ~IRQ_WORK_PENDING;

	for (;;) {

		nflags = flags | IRQ_WORK_CLAIMED;

		oflags = cmpxchg(&work->flags, flags, nflags);

		oflags = atomic_cmpxchg(&work->flags, flags, nflags);

		if (oflags == flags)

			break;

		if (oflags & IRQ_WORK_PENDING)
@@ -61,7 +61,7 @@ void __weak arch_irq_work_raise(void) 
static void __irq_work_queue_local(struct irq_work *work)

{

	/* If the work is "lazy", handle it from next tick if any */

	if (work->flags & IRQ_WORK_LAZY) {

	if (atomic_read(&work->flags) & IRQ_WORK_LAZY) {

		if (llist_add(&work->llnode, this_cpu_ptr(&lazy_list)) &&

		    tick_nohz_tick_stopped())

			arch_irq_work_raise();
@@ -143,7 +143,7 @@ static void irq_work_run_list(struct llist_head *list) 
{

	struct irq_work *work, *tmp;

	struct llist_node *llnode;

	unsigned long flags;

	int flags;



	BUG_ON(!irqs_disabled());
@@ -159,15 +159,15 @@ static void irq_work_run_list(struct llist_head *list) 
		 * to claim that work don't rely on us to handle their data

		 * while we are in the middle of the func.

		 */

		flags = work->flags & ~IRQ_WORK_PENDING;

		xchg(&work->flags, flags);

		flags = atomic_read(&work->flags) & ~IRQ_WORK_PENDING;

		atomic_xchg(&work->flags, flags);



		work->func(work);

		/*

		 * Clear the BUSY bit and return to the free state if

		 * no-one else claimed it meanwhile.

		 */

		(void)cmpxchg(&work->flags, flags, flags & ~IRQ_WORK_BUSY);

		(void)atomic_cmpxchg(&work->flags, flags, flags & ~IRQ_WORK_BUSY);

	}

}
@@ -199,7 +199,7 @@ void irq_work_sync(struct irq_work *work) 
{

	lockdep_assert_irqs_enabled();



	while (work->flags & IRQ_WORK_BUSY)

	while (atomic_read(&work->flags) & IRQ_WORK_BUSY)

		cpu_relax();

}

EXPORT_SYMBOL_GPL(irq_work_sync);

kernel/printk/printk.c

+1 −1
Original line number Diff line number Diff line
@@ -2961,7 +2961,7 @@ static void wake_up_klogd_work_func(struct irq_work *irq_work) 


static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {

	.func = wake_up_klogd_work_func,

	.flags = IRQ_WORK_LAZY,

	.flags = ATOMIC_INIT(IRQ_WORK_LAZY),

};



void wake_up_klogd(void)

kernel/trace/bpf_trace.c

+1 −1
Original line number Diff line number Diff line
@@ -660,7 +660,7 @@ BPF_CALL_1(bpf_send_signal, u32, sig) 
			return -EINVAL;



		work = this_cpu_ptr(&send_signal_work);

		if (work->irq_work.flags & IRQ_WORK_BUSY)

		if (atomic_read(&work->irq_work.flags) & IRQ_WORK_BUSY)

			return -EBUSY;



		/* Add the current task, which is the target of sending signal,

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