linux-kernel - [RFC 2/6] softirq: Introduce mask for __do

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Message-Id: <20180118161238.13792-3-dima@arista.com>
Date:   Thu, 18 Jan 2018 16:12:34 +0000
From:   Dmitry Safonov <dima@...sta.com>
To:     linux-kernel@...r.kernel.org
Cc:     Dmitry Safonov <dima@...sta.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Miller <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        Ingo Molnar <mingo@...nel.org>,
        "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Mauro Carvalho Chehab <mchehab@...pensource.com>,
        Mike Galbraith <efault@....de>,
        Paolo Abeni <pabeni@...hat.com>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Radu Rendec <rrendec@...sta.com>,
        Rik van Riel <riel@...hat.com>,
        Stanislaw Gruszka <sgruszka@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Wanpeng Li <wanpeng.li@...mail.com>
Subject: [RFC 2/6] softirq: Introduce mask for __do_softirq()

__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@...sta.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