Please have a look at the patch below.

Taking this opportunity, in addition:
- I removed the unnecessary barrier() from __clear_bit_unlock().
  ia64_st4_rel_nta() makes sure all the modifications are globally
  seen before the bit is seen to be off.
- I made __clear_bit() modeled after __set_bit() and __change_bit().
- I corrected some comments sating that a memory barrier is provided,
  yet in reality, it is the acquisition side of the memory barrier only.
- I corrected some comments, e.g. test_and_clear_bit() was peaking
  about "bit to set".

Here is the code generated from my and the old versions.
(Though I do not know why "and" is moved in the 2nd bundle.):

test_new()
{
        __clear_bit_unlock(3, &data);
}

test_old()
{
        old__clear_bit_unlock(3, &data);
}

0000000000000000 <test_new>:
   0:   02 00 00 00 01 00       [MII]       nop.m 0x0
   6:   e0 00 04 00 48 00                   addl r14=0,r1;;
   c:   00 00 04 00                         nop.i 0x0
  10:   0b 10 00 1c 10 10       [MMI]       ld4 r2=[r14];;
  16:   f0 b8 0b 58 44 00                   and r15=-9,r2
  1c:   00 00 04 00                         nop.i 0x0;;
  20:   0a 00 3c 1c b6 11       [MMI]       st4.rel.nta [r14]=r15;;
  26:   00 00 00 02 00 00                   nop.m 0x0
  2c:   01 70 00 84                         mov r8=r14
  30:   1d 00 00 00 01 00       [MFB]       nop.m 0x0
  36:   00 00 00 02 00 80                   nop.f 0x0
  3c:   08 00 84 00                         br.ret.sptk.many b0;;

0000000000000040 <test_old>:
  40:   02 00 00 00 01 00       [MII]       nop.m 0x0
  46:   e0 00 04 00 48 00                   addl r14=0,r1;;
  4c:   00 00 04 00                         nop.i 0x0
  50:   03 10 00 1c b0 10       [MII]       ld4.acq r2=[r14]
  56:   00 00 00 02 00 e0                   nop.i 0x0;;
  5c:   71 17 b0 88                         and r15=-9,r2;;
  60:   0a 00 3c 1c b6 11       [MMI]       st4.rel.nta [r14]=r15;;
  66:   00 00 00 02 00 00                   nop.m 0x0
  6c:   01 70 00 84                         mov r8=r14
  70:   1d 00 00 00 01 00       [MFB]       nop.m 0x0
  76:   00 00 00 02 00 80                   nop.f 0x0
  7c:   08 00 84 00                         br.ret.sptk.many b0;;

Signed-off-by: Zoltan Menyhart, <Zoltan.Menyhart@bull.net>

Thanks,

Zoltan Menyhart