[parisc-linux] ldcw in __pthread_acquire

[Matthew Wilcox]

On Fri, Dec 15, 2000 at 10:37:55PM +1100, Alan Modra wrote:
> On Fri, 15 Dec 2000, John Marvin wrote:
> 
> > 
> > I just ran into an unaligned data reference in user land.  The problem is
> > that the routine __pthread_acquire (in libpthread) does a ldcw, but it is
> > not ensuring that the address it is operating on is 16 byte aligned (it is
> > operating on the address that was passed in as the first argument).  Some
> > processors don't require the 16 byte alignment, but many do.

> Here's where the problem is:
> 
> glibc/linuxthreads/sysdeps/pthread/bits/pthreadtypes.h
> 
> struct _pthread_fastlock
> {
>   long int __status;   /* "Free" or "taken" or head of waiting list */
>   int __spinlock;      /* Used by compare_and_swap emulation. Also,
> 			  adaptive SMP lock stores spin count here. */
> };

Can we move the __spinlock to be the first element of the struct,
and then mark the struct as requiring 16-byte alignment?  i have the
feeling this might `just work', since most structs will be allocated at
16-byte-aligned addresses anyway.

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