On Wed, Dec 13, 2006 at 11:02:48AM +0100, Zoltan Menyhart wrote: > I like this code with the following slight modifications: > - let's keep "m" as pointer to volatile Why? What benefit is there to doing an ld4.acq instead of a plain ld4? > - let's keep on using "__u32" types Why be so ugly? > - not sure we need "new" Good idea. > - return the old bit I don't understand what you mean here. > volatile __u32 *m = (volatile __u32 *)addr + (nr >> 5); > __u32 bit = 1 << (nr & 31); > > __u32 old = *m; > while (!(old & bit)) { > __u32 prev = cmpxchg_acq(m, old, old | bit); > CMPXCHG_BUGCHECK(m); > if (prev == old) > return 0; > old = prev; > } > return 1; > > It compiles to: > > 0: and r15=31,r32 > 6: mov r14=1 > c: extr r32=r32,5,27;; > 10: shladd r18=r32,2,r33;; > 16: ld4.acq r16=[r18] > 1c: shl r17=r14,r15;; > 20: and r14=r17,r16;; > 26: nop.m 0x0 > 2c: cmp4.eq p7,p6=0,r14 > 30: nop.b 0x0 > 36: nop.b 0x0 > 3c: (p06) br.cond.dpnt.few a0 <+0xa0> > 40: nop.m 0x0 > 46: zxt4 r14=r16 > 4c: nop.b 0x0;; > 50: mov.m ar.ccv=r14;; > 56: nop.m 0x0 > 5c: or r14=r17,r16 > 60: nop.m 0x0;; > 66: cmpxchg4.acq r14=[r18],r14,ar.ccv > 6c: nop.i 0x0;; > 70: cmp4.eq p7,p6=r14,r16 > 76: nop.f 0x0 > 7c: and r15=r17,r14 > 80: mov r16=r14 > 86: nop.f 0x0 > 8c: (p07) br.cond.dpnt.few b0 <+0xb0>;; > 90: nop.m 0x0 > 96: cmp4.eq p7,p6=0,r15 > 9c: (p07) br.cond.dptk.few 40 <+0x40> > a0: nop.m 0x0 > a6: mov r8=1 > ac: br.ret.sptk.many b0;; > b0: nop.m 0x0 > b6: mov r8=r0 > bc: br.ret.sptk.many b0;; > > It seems to be o.k., thanks. > > Zolt?n Menyh?rt > - To unsubscribe from this list: 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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