J. Bruce Fields wrote: > On Mon, Jun 23, 2008 at 09:58:21PM -0500, Tom Tucker wrote: >> J. Bruce Fields wrote: >>> On Sat, Jun 21, 2008 at 11:31:43AM -0500, Tom Tucker wrote: >>> >>>> J. Bruce Fields wrote: >>>> >>>>> On Thu, May 29, 2008 at 12:54:46PM -0500, Tom Tucker wrote: >>>>>> diff --git a/net/sunrpc/xprtrdma/svc_rdma.c b/net/sunrpc/xprtrdma/svc_rdma.c >>>>>> index 88c0ca2..545ea72 100644 >>>>>> --- a/net/sunrpc/xprtrdma/svc_rdma.c >>>>>> +++ b/net/sunrpc/xprtrdma/svc_rdma.c >>>>>> @@ -69,6 +69,9 @@ atomic_t rdma_stat_rq_prod; >>>>>> atomic_t rdma_stat_sq_poll; >>>>>> atomic_t rdma_stat_sq_prod; >>>>>> +/* Temporary NFS request map cache */ >>>>>> +struct kmem_cache *svc_rdma_map_cachep = NULL; >>>>>> >>>>> No need to initialize globals to NULL. >>>>> >>>>> >>>> I thought only static objects were initialized per the C standard. Or >>>> are you saying that this particular >>>> global doesn't need to be initialized because of the way it is used? >>>> >>> I don't know if the initialization is mandated by the standards or >>> whether it's just gcc behavior, but I know I get a complaint every time >>> somebody finds one of those.... The implicit initialization to zero was defined back then by K&R: http://www.cs.utah.edu/~phister/K_n_R/chapter4.html#s4.9 "In the absence of explicit initialization, external and static variables are guaranteed to be initialized to zero" AFAIK this convention was kept by the C standards ever since. >>> >>> >> In this case, the initialization is unnecessary, so it can be safely dumped. >> >>> That may partly just be a preference for conciseness, but I think it may >>> also allow gcc to put the thing in a different section and save some >>> space in the on-disk kernel--I don't know. >>> >>> >> Right -- un-initialized data goes in a different section, the .bss >> section in particular. Since the .bss section is not "initialized", >> there are no values (zeroes in this case) sitting in the object file >> ready to be mapped into whatever location becomes .bss. By contrast, the >> .data section contains initialized data and the initial values are >> sitting in the object file. >> >> So my question here is a little subtler: >> >> A. Do we discard _all_ zero initializations of non-static globals >> because we can safely assume that .bss is initialzed (not a fan of >> this), or Also static locals... What matters is that the variable has static allocation, its scope is irrelevant to the initialization issue. Benny >> >> B. Don't be an idiot and initialize objects unnecessarily because it >> bloats the kernel object file? >> >> An idiot voting for B, > > My understanding is that it's A--e.g. checkpatch.pl has a dumb regex > that just checks for these assignments and whines about them however > they're used. > > Google doesn't find me any more detailed discussion of the policy. > > --b. > -- > To unsubscribe from this list: send the line "unsubscribe linux-nfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
