Commit e48c15b7 authored Jun 29, 2020 by Paul E. McKenney

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@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

parent 160c7ba3

include/linux/smp.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -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;

include/linux/smp_types.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -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 */

kernel/smp.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -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);
		}

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