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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: Frederic 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Frederic Weisbecker 2019-11-08 17:08:55 +01:00 committed by Ingo Molnar
parent 31f4f5b495
commit 153bedbac2
5 changed files with 19 additions and 15 deletions
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10
include/linux/irq_work.h
View File

@ -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);

2
kernel/bpf/stackmap.c
View File

@ -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;
}

18
kernel/irq_work.c
View File

@ -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);

2
kernel/printk/printk.c
View File

@ -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)

2
kernel/trace/bpf_trace.c
View File

@ -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,