[RFC 2/6] softirq: Introduce mask for __do_softirq()

Dmitry Safonov
2018-01-18T16:12:50Z

__do_softirq() serves all pending softirqs.
As we need to separate softirqs by different groups, we need to serve
softirqs from one group and deffer softirqs from the other.
Change __do_softirq() so it'll have a mask of softirqs it needs to
serve instead of servicing all pending softirqs.

Signed-off-by: Dmitry Safonov <dima@arista.com>
---
include/linux/interrupt.h | 8 ++++----
kernel/softirq.c | 27 ++++++++++++++-------------
2 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 5bb6b435f0bb..2ea09896bd6e 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -490,14 +490,14 @@ struct softirq_action
};

asmlinkage void do_softirq(void);
-asmlinkage void __do_softirq(void);
+asmlinkage void __do_softirq(__u32 mask);

#ifdef __ARCH_HAS_DO_SOFTIRQ
-void do_softirq_own_stack(void);
+void do_softirq_own_stack(__u32 mask);
#else
-static inline void do_softirq_own_stack(void)
+static inline void do_softirq_own_stack(__u32 mask)
{
- __do_softirq();
+ __do_softirq(mask);
}
#endif

diff --git a/kernel/softirq.c b/kernel/softirq.c
index c9aecdd57107..ca8c3db4570d 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -240,7 +240,7 @@ static inline bool lockdep_softirq_start(void) { return false; }
static inline void lockdep_softirq_end(bool in_hardirq) { }
#endif

-asmlinkage __visible void __softirq_entry __do_softirq(void)
+asmlinkage __visible void __softirq_entry __do_softirq(__u32 mask)
{
unsigned long end = jiffies + MAX_SOFTIRQ_TIME;
unsigned long old_flags = current->flags;
@@ -265,7 +265,8 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)

restart:
/* Reset the pending bitmask before enabling irqs */
- set_softirq_pending(0);
+ set_softirq_pending(pending & ~mask);
+ pending &= mask;

local_irq_enable();

@@ -299,7 +300,7 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
local_irq_disable();

pending = local_softirq_pending();
- if (pending) {
+ if (pending & mask) {
if (time_before(jiffies, end) && !need_resched() &&
--max_restart)
goto restart;
@@ -316,18 +317,16 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)

asmlinkage __visible void do_softirq(void)
{
- __u32 pending;
+ __u32 pending = local_softirq_pending();
unsigned long flags;

- if (in_interrupt())
+ if (in_interrupt() || !pending)
return;

local_irq_save(flags);

- pending = local_softirq_pending();
-
- if (pending && !ksoftirqd_running())
- do_softirq_own_stack();
+ if (!ksoftirqd_running())
+ do_softirq_own_stack(pending);

local_irq_restore(flags);
}
@@ -353,7 +352,9 @@ void irq_enter(void)

static inline void invoke_softirq(void)
{
- if (ksoftirqd_running())
+ __u32 pending = local_softirq_pending();
+
+ if (!pending || !ksoftirqd_running())
return;

if (!force_irqthreads) {
@@ -363,14 +364,14 @@ static inline void invoke_softirq(void)
* it is the irq stack, because it should be near empty
* at this stage.
*/
- __do_softirq();
+ __do_softirq(pending);
#else
/*
* Otherwise, irq_exit() is called on the task stack that can
* be potentially deep already. So call softirq in its own stack
* to prevent from any overrun.
*/
- do_softirq_own_stack();
+ do_softirq_own_stack(pending);
#endif
} else {
wakeup_softirqd();
@@ -679,7 +680,7 @@ static void run_ksoftirqd(unsigned int cpu)
* We can safely run softirq on inline stack, as we are not deep
* in the task stack here.
*/
- __do_softirq();
+ __do_softirq(~0);
local_irq_enable();
cond_resched_rcu_qs();
return;
--
2.13.6