linux-kernel - [tip: core/rcu] smp: Add source and destination CPUs to __call_single

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Date:   Fri, 09 Oct 2020 06:35:08 -0000
From:   "tip-bot2 for Paul E. McKenney" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Frederic Weisbecker <frederic@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: core/rcu] smp: Add source and destination CPUs to __call_single_data

The following commit has been merged into the core/rcu branch of tip:

Commit-ID:     e48c15b796d412ede883bb2ef7779b2a142f7962
Gitweb:        https://git.kernel.org/tip/e48c15b796d412ede883bb2ef7779b2a142f7962
Author:        Paul E. McKenney <paulmck@...nel.org>
AuthorDate:    Mon, 29 Jun 2020 17:21:32 -07:00
Committer:     Paul E. McKenney <paulmck@...nel.org>
CommitterDate: Fri, 04 Sep 2020 11:50:50 -07:00

smp: Add source and destination CPUs to __call_single_data

This commit adds a destination CPU to __call_single_data, and is inspired
by an earlier commit by Peter Zijlstra.  This version adds #ifdef to
permit use by 32-bit systems and supplying the destination CPU for all
smp_call_function*() requests, not just smp_call_function_single().

If need be, 32-bit systems could be accommodated by shrinking the flags
field to 16 bits (the atomic_t variant is currently unused) and by
providing only eight bits for CPU on such systems.

It is not clear that the addition of the fields to __call_single_node
are really needed.

[ paulmck: Apply Boqun Feng feedback on 32-bit builds. ]
Link: https://lore.kernel.org/lkml/20200615164048.GC2531@hirez.programming.kicks-ass.net/
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: Frederic Weisbecker <frederic@...nel.org>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 include/linux/smp.h       | 3 +++
 include/linux/smp_types.h | 3 +++
 kernel/smp.c              | 6 ++++++
 3 files changed, 12 insertions(+)

diff --git a/include/linux/smp.h b/include/linux/smp.h
index 80d557e..9f13966 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -26,6 +26,9 @@ struct __call_single_data {
 		struct {
 			struct llist_node llist;
 			unsigned int flags;
+#ifdef CONFIG_64BIT
+			u16 src, dst;
+#endif
 		};
 	};
 	smp_call_func_t func;
diff --git a/include/linux/smp_types.h b/include/linux/smp_types.h
index 364b3ae..2e8461a 100644
--- a/include/linux/smp_types.h
+++ b/include/linux/smp_types.h
@@ -61,6 +61,9 @@ struct __call_single_node {
 		unsigned int	u_flags;
 		atomic_t	a_flags;
 	};
+#ifdef CONFIG_64BIT
+	u16 src, dst;
+#endif
 };
 
 #endif /* __LINUX_SMP_TYPES_H */
diff --git a/kernel/smp.c b/kernel/smp.c
index d0ae8eb..865a876 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -375,6 +375,9 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
 
 	csd->func = func;
 	csd->info = info;
+#ifdef CONFIG_64BIT
+	csd->dst = cpu;
+#endif
 
 	err = generic_exec_single(cpu, csd);
 
@@ -540,6 +543,9 @@ static void smp_call_function_many_cond(const struct cpumask *mask,
 			csd->flags |= CSD_TYPE_SYNC;
 		csd->func = func;
 		csd->info = info;
+#ifdef CONFIG_64BIT
+		csd->dst = cpu;
+#endif
 		if (llist_add(&csd->llist, &per_cpu(call_single_queue, cpu)))
 			__cpumask_set_cpu(cpu, cfd->cpumask_ipi);
 	}