Re: [Xen-devel] [PATCHv2 3/6] xen: generic xadd() for ticket locks

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Thu, 2015-04-16 at 16:28 +0100, Jan Beulich wrote:
> >>> On 10.04.15 at 16:19, <david.vrabel@xxxxxxxxxx> wrote:
> > +#define xadd(ptr, v) generic_xaddl((ptr), (v))
> 
> I think it is at least confusing to call the thing xadd (looking to be
> size generic) and then expand to generic_xaddl (only supporting
> 32-bit operations), yet subsequently implementing a size-generic
> xadd() for x86.

Indeed, and I went to build on arm32 prior to hacking up a proper xadd
and:

spinlock.c: In function â_spin_lockâ:
spinlock.c:145:5: error: passing argument 1 of âgeneric_xaddlâ from 
incompatible pointer type [-Werror]
     tickets.head_tail = xadd(&lock->tickets, tickets.head_tail);
     ^
spinlock.c:15:12: note: expected âvolatile u32 *â but argument is of type 
âunion spinlock_tickets_t *â
 static u32 generic_xaddl(volatile u32 *ptr, u32 v)
            ^

(I hope to knock up the arm asm version in the next hour or so, so you
may not care...)

Ian.


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