Christoph Lameter wrote on Tuesday, March 28, 2006 3:48 PM > Could we simply define these smb_mb__*_clear_bit to be noops > and then make the atomic bit ops to have full barriers? That would satisfy > Nick's objections. Oh, it also penalize all other 1,055 call site of clear_bit(), though I don't know how many actually needs memory barrier. I suspect some need "lock" barrier, some need "unlock" barrier, and of course some needs full fence. Why not make unlock_buffer use test_and_clear_bit()? Utilizing it's implied full memory fence and throw away the return value? OK, OK, this is obscured. Then introduce clear_bit_memory_fence API or some sort. - Ken diff -Nurp linux-2.6.16/fs/buffer.c linux-2.6.16.ken/fs/buffer.c --- linux-2.6.16/fs/buffer.c 2006-03-19 21:53:29.000000000 -0800 +++ linux-2.6.16.ken/fs/buffer.c 2006-03-28 17:20:02.000000000 -0800 @@ -78,8 +78,7 @@ EXPORT_SYMBOL(__lock_buffer); void fastcall unlock_buffer(struct buffer_head *bh) { - clear_buffer_locked(bh); - smp_mb__after_clear_bit(); + test_clear_buffer_locked(bh); wake_up_bit(&bh->b_state, BH_Lock); } - : send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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