RE: [PATCH] locking/atomic: Make test_and_*_bit() ordered on failure

...

p += BIT_WORD(nr);

• if (READ_ONCE(*p) & mask)

• return 1;
  

• old = arch_atomic_long_fetch_or(mask, (atomic_long_t *)p); return !!(old & mask);

}

This looks like the same pattern (attempting to avoid a locked bus cycle) that caused the qdisc code to sit on transmit packets (even on x86). That had some barriers in it (possibly nops on x86) that didn't help - although the comments suggested otherwise.

I wonder if the pattern has been used anywhere else?

David

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