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From:   Frederic Weisbecker <frederic@kernel.org>
To:     LKML <linux-kernel@vger.kernel.org>
Cc:     Frederic Weisbecker <fweisbec@gmail.com>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        "David S . Miller" <davem@davemloft.net>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Frederic Weisbecker <frederic@kernel.org>,
        "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
        Ingo Molnar <mingo@kernel.org>,
        Mauro Carvalho Chehab <mchehab@s-opensource.com>
Subject: [RFC PATCH 28/30] softirq: Disable vector on execution
Date:   Thu, 11 Oct 2018 01:12:15 +0200
Message-Id: <1539213137-13953-29-git-send-email-frederic@kernel.org>
In-Reply-To: <1539213137-13953-1-git-send-email-frederic@kernel.org>
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From: Frederic Weisbecker <fweisbec@gmail.com>

Disable a vector while it is being processed. This prepare for softirq
re-entrancy with an obvious single constraint: a vector can't be
interrupted by itself.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 kernel/softirq.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 3efa59e..457bf60 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -357,7 +357,10 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
 		kstat_incr_softirqs_this_cpu(vec_nr);
 
 		trace_softirq_entry(vec_nr);
+		softirq_enabled_nand(BIT(vec_nr));
+		barrier();
 		h->action(h);
+		softirq_enabled_or(BIT(vec_nr));
 		trace_softirq_exit(vec_nr);
 		if (unlikely(prev_count != preempt_count())) {
 			pr_err("huh, entered softirq %u %s %p with preempt_count %08x, exited with %08x?\n",
-- 
2.7.4