Re: [PATCH] Update to new generic semaphore algorithm v2

[Torvald Riegel <triegel at redhat dot com>]

On Thu, 2015-01-22 at 08:54 -0800, Steve Ellcey wrote:
> On Tue, 2015-01-13 at 02:15 +0100, Torvald Riegel wrote:
> > This patch is a revision of that patch:
> > https://sourceware.org/ml/libc-alpha/2014-12/msg00527.html
> > 
> > OK?
> 
> > 2015-01-13  Torvald Riegel  <triegel@redhat.com>
> > 
> > 	[BZ #12674]
> > 	* nptl/sem_waitcommon.c: New file.  Implement new semaphore algorithm.
> 
> 
> Torvald,  I think this patch has broken the MIPS build.  I get a bunch
> of failures, they start with the new file (sem_waitcommon.c).  It looks
> like some kind of 32/64 bit issue with the size of semaphores.  Any
> ideas on how to fix this?
> 
> In file included from ../sysdeps/nptl/lowlevellock.h:22:0,
>                  from ../nptl/descr.h:30,
>                  from ../sysdeps/mips/nptl/tls.h:73,
>                  from ../include/errno.h:27,
>                  from sem_waitcommon.c:20,
>                  from sem_wait.c:20:
> sem_waitcommon.c: In function ï~@~X__sem_wait_cleanupï~@~Y:
> sem_waitcommon.c:190:47: error: left shift count >= width of type
> [-Werror=shift-count-overflow]
>    atomic_fetch_add_relaxed (&sem->data, -(1UL << SEM_NWAITERS_SHIFT));
>                                                ^
> ../include/atomic.h:617:31: note: in definition of macro
> ï~@~Xatomic_fetch_add_relaxedï~@~Y
>    __atomic_fetch_add ((mem), (operand), __ATOMIC_RELAXED); })
>                                ^
> sem_waitcommon.c: In function ï~@~X__new_sem_wait_slowï~@~Y:
> sem_waitcommon.c:267:11: error: left shift count >= width of type
> [-Werror=shift-count-overflow]
>        1UL << SEM_NWAITERS_SHIFT);

Do you use an LP64 data model?  "1UL" is 64b if LP64, and
SEM_NWAITERS_SHIFT is 32.  You could try 1ULL instead to see whether
that makes a difference.
The semaphore code uses the 64b version, because atomic.h thinks 64b
atomic ops are available.

Which compiler do you use?