Messages in this thread | | | Subject | Re: [PATCH] x86: Add kerneldoc for pcommit_sfence() | From | Ross Zwisler <> | Date | Fri, 13 Mar 2015 14:03:13 -0600 |
| |
On Thu, 2015-03-12 at 11:58 +0100, Ingo Molnar wrote: > > > +/** > > > + * pcommit_sfence() - persistent commit and fence > > > + * > > > + * The pcommit instruction ensures that data that has been flushed from the > > > + * processor's cache hierarchy with clwb, clflushopt or clflush is accepted to > > > + * memory and is durable on the DIMM. The primary use case for this is > > > + * persistent memory. > > Please capitalize canonical instruction names like the CPU makers do, > so that they stand out better in free flowing English text, i.e. > something like: > > * > * The PCOMMIT instruction ensures that data that has been flushed from the > * processor's cache hierarchy with CLWB, CLFLUSHOPT or CLFLUSH is accepted to > * memory and is durable on the DIMM. The primary use case for this is > * persistent memory.
Sure, will do.
> > > + * void flush_and_commit_buffer(void *vaddr, unsigned int size) > > > + * { > > > + * unsigned long clflush_mask = boot_cpu_data.x86_clflush_size - 1; > > > + * char *vend = (char *)vaddr + size; > > So here we cast vaddr to (char *) - which is unnecessary, as 'void *' > has byte granular pointer arithmetics. > > And 'vend' should be void *' to begin with, to match the type > of 'vaddr'.
The original version, copied in part from clflush_cache_range, did do everything with void* pointers. I changed it to use char* pointers based on feedback from hpa. :)
It seems like both have arguments for them. Char pointer arithmetic has the advantage that its behavior is standard in C, so it's not specific to gcc. I agree that void* has the advantage that it fits more naturally with the types of the parameters passed in, requiring no casting.
I honestly don't feel strongly either way - please let me know what you guys prefer in the x86 arch code.
> > > + * for (p = (char *)((unsigned long)vaddr & ~clflush_mask); > > > + * p < vend; p += boot_cpu_data.x86_clflush_size) > > > + * clwb(p); > > > + * > > > + * // sfence to order clwb/clflushopt/clflush cache flushes > > > + * // mfence via mb() also works > > Yeah so this isn't a C++ kernel, thank all the 3000+ gods and other > supreme beings worshipped on this planet!
Yep. C++ style // comments are happily accepted by gcc in C code, though, and this was my attempt to get around the fact that /* */ style comments can't be nested. I couldn't think of a more elegant way of having code + comments in a kerneldoc comment. I agree that if this code were ever to be pulled out and used, the comment style would need to be corrected to be the standard kernel style.
> Also please put 'vaddr' into single quotes, to make the parameter name > stand out better in written text: > > > > + * After this function completes the data pointed to by 'vaddr' has been
Sure.
Thanks, - Ross
| |