Commit a1f10661 authored by Ahmed S. Darwish's avatar Ahmed S. Darwish Committed by Peter Zijlstra
Browse files

x86/tsc: Use seqcount_latch_t 



Latch sequence counters have unique read and write APIs, and thus
seqcount_latch_t was recently introduced at seqlock.h.

Use that new data type instead of plain seqcount_t. This adds the
necessary type-safety and ensures that only latching-safe seqcount APIs
are to be used.

Signed-off-by: default avatarAhmed S. Darwish <a.darwish@linutronix.de>
[peterz: unwreck cyc2ns_read_begin()]
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200827114044.11173-7-a.darwish@linutronix.de
parent 249d0538

arch/x86/kernel/tsc.c

+5 −5
Original line number Diff line number Diff line
@@ -54,7 +54,7 @@ struct clocksource *art_related_clocksource; 


struct cyc2ns {

	struct cyc2ns_data data[2];	/*  0 + 2*16 = 32 */

	seqcount_t	   seq;		/* 32 + 4    = 36 */

	seqcount_latch_t   seq;		/* 32 + 4    = 36 */



}; /* fits one cacheline */
@@ -73,14 +73,14 @@ __always_inline void cyc2ns_read_begin(struct cyc2ns_data *data) 
	preempt_disable_notrace();



	do {

		seq = this_cpu_read(cyc2ns.seq.sequence);

		seq = this_cpu_read(cyc2ns.seq.seqcount.sequence);

		idx = seq & 1;



		data->cyc2ns_offset = this_cpu_read(cyc2ns.data[idx].cyc2ns_offset);

		data->cyc2ns_mul    = this_cpu_read(cyc2ns.data[idx].cyc2ns_mul);

		data->cyc2ns_shift  = this_cpu_read(cyc2ns.data[idx].cyc2ns_shift);



	} while (unlikely(seq != this_cpu_read(cyc2ns.seq.sequence)));

	} while (unlikely(seq != this_cpu_read(cyc2ns.seq.seqcount.sequence)));

}



__always_inline void cyc2ns_read_end(void)
@@ -186,7 +186,7 @@ static void __init cyc2ns_init_boot_cpu(void) 
{

	struct cyc2ns *c2n = this_cpu_ptr(&cyc2ns);



	seqcount_init(&c2n->seq);

	seqcount_latch_init(&c2n->seq);

	__set_cyc2ns_scale(tsc_khz, smp_processor_id(), rdtsc());

}
@@ -203,7 +203,7 @@ static void __init cyc2ns_init_secondary_cpus(void) 


	for_each_possible_cpu(cpu) {

		if (cpu != this_cpu) {

			seqcount_init(&c2n->seq);

			seqcount_latch_init(&c2n->seq);

			c2n = per_cpu_ptr(&cyc2ns, cpu);

			c2n->data[0] = data[0];

			c2n->data[1] = data[1];

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