Re: [PATCH] fs/netfs: Remove redundant use of smp_rmb()

From: David Howells
Date: Sat Dec 07 2024 - 03:05:15 EST


Akira Yokosawa <akiyks@xxxxxxxxx> wrote:

> Are you sure removing the smp_rmb() is realy the right thing to do?

The wait_on_bit*() class functions, e.g.:

wait_on_bit(unsigned long *word, int bit, unsigned mode)
{
might_sleep();
if (!test_bit_acquire(bit, word))
return 0;
return out_of_line_wait_on_bit(word, bit,
bit_wait,
mode);
}

now unconditionally includes an appropriate barrier on the test_bit(), so the
smp_rmb() should be unnecessary, though netfslib should probably be using
clear_and_wake_up_bit().

Probably we need to update the doc to reflect this.

David