Hello, Peter,
The ring-buffer code uses control dependencies, and the shiny new
READ_ONCE_CTRL() is now in mainline. I was idly curious about whether
the write side could use smp_store_release(), and I found this:
static inline void perf_mmap__write_tail(struct perf_mmap *md, u64 tail)
{
struct perf_event_mmap_page *pc = md->base;
/*
* ensure all reads are done before we write the tail out.
*/
mb();
pc->data_tail = tail;
}
I see mb() rather than smp_mb(). Did I find the correct code for the
write side? If so, why mb() rather than smp_mb()? To serialize against
MMIO interactions with hardware counters or some such?
Thanx, Paul
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