From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Date: Thu, 28 Sep 2006 07:05:16 +0000 Subject: Re: 2.6.18 perfmon new code base + libpfm + pfmon Message-Id: <20060928000516.1a0aaca0.akpm@osdl.org> List-Id: References: <20060926143420.GF14550@frankl.hpl.hp.com> <20060926220951.39bd344f.akpm@osdl.org> <20060927224832.GA17883@frankl.hpl.hp.com> <20060927163100.e83a1f79.akpm@osdl.org> <20060928064949.GA18245@frankl.hpl.hp.com> In-Reply-To: <20060928064949.GA18245@frankl.hpl.hp.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: eranian@hpl.hp.com Cc: perfmon@napali.hpl.hp.com, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org On Wed, 27 Sep 2006 23:49:49 -0700 Stephane Eranian wrote: > Andrew, > > On Wed, Sep 27, 2006 at 04:31:00PM -0700, Andrew Morton wrote: > > > > > > Here is the summary of the various point raised by your review and the current > > > status. I am hoping to close all points by next release. > > > > > > ... > > > > > > [akpm]: use fget_light() in some place instead of fget() > > > - not sure understand when to use one versus the other > > > > > > > They are always interchangeable. fget_light() is simply an optimised, > > messier-to-use version. > > What are exactly the assumptions of fget_light()? Just the ones in the comment, really - it assumes that the caller has a single ref on the file. ie: we're within a system call which passed in an fd, or within a pagefault and this file* is current->mm->some_vma->vm_file. You _might_ get into trouble if using it against some file* which belongs to a different process, and if you don't already have a ref on that file*. But that's usually a bug anyway, unless the code is aware of and is exploiting the RCU management of these things. There are lots of example usages around the place. > > > > > > > > .. > > > > > > [akpm]: carta_random32() should be in another header file > > > - yes, I know. Should I create a specific header file? I don't think random.h > > > is meant for this. > > > > I suppose so. Or just stick the declaration into kernel.h. > > > > I had a patch go past the other day which had a hand-rolled > > fast-but-not-very-good pseudo random number generator in it. I couldn't > > remember where I'd seen one, and now I can't remember what patch it was > > that needed it. Sigh. > > > > Anyway, a standalone patch which adds that function into lib/whatever.c > > would be nice. > > I will post a standalone patch for carta random. I can provide a standalone header > file in include/linux/carta_random.h. Thanks.