Messages in this thread | | | Date | Thu, 30 Sep 2010 23:23:39 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 05/17] fs: icache lock i_count |
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On Fri, 1 Oct 2010 02:16:02 -0400 Christoph Hellwig <hch@infradead.org> wrote:
> On Thu, Sep 30, 2010 at 11:04:16PM -0700, Andrew Morton wrote: > > No, we've run into problems *frequently*. A common case is where we > > convert a mutex to a spinlock or vice versa. If you don't rename the > > lock, the code still compiles (with warnings) and crashes horridly at > > runtime. > > Sorry, if you run code with that obvious warnings you beg for trouble. > If you really believe your advanced users arw too stupid to read > compiler warnings enforcing -Werror is for sure better than obsfucating > the code.
Well, it has happened, fairly regularly. A common scenario is where someone has done a conversion in one tree and someone else has touched overlapping code in another tree and when the two meet in linux-next, splat. Renaming the field simply eliminates this.
Of course, the warnings don't get noticed because of the enormous warning storm which a kernel build produces (generally much worse on non-x86, btw).
Another reason for remaining a field is when we desire that it henceforth be accessed via accessor functions - renaming it will reliably break any unconverted code.
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