Commit d3b35b87 authored Jul 20, 2020 by Ahmed S. Darwish Committed by Peter Zijlstra Jul 29, 2020

seqlock: seqcount_t latch: End read sections with read_seqcount_retry()



The seqcount_t latch reader example at the raw_write_seqcount_latch()
kernel-doc comment ends the latch read section with a manual smp memory
barrier and sequence counter comparison.

This is technically correct, but it is suboptimal: read_seqcount_retry()
already contains the same logic of an smp memory barrier and sequence
counter comparison.

End the latch read critical section example with read_seqcount_retry().

Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200720155530.1173732-4-a.darwish@linutronix.de

parent 15cbe67b

include/linux/seqlock.h

+2 −2

Original line number	Diff line number	Diff line
		@@ -363,8 +363,8 @@ static inline int raw_read_seqcount_latch(seqcount_t *s)
		* idx = seq & 0x01;
		* entry = data_query(latch->data[idx], ...);
		*
		* smp_rmb();
		* } while (seq != latch->seq);
		* // read_seqcount_retry() includes needed smp_rmb()
		* } while (read_seqcount_retry(&latch->seq, seq));
		*
		* return entry;
		* }

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