Messages in this thread | | | Date | Tue, 17 Nov 2020 11:31:47 -0500 | From | Mike Snitzer <> | Subject | Re: md: dm-writeback: add __noreturn to BUG-ging function |
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On Mon, Nov 16 2020 at 6:00pm -0500, Randy Dunlap <rdunlap@infradead.org> wrote:
> On 11/15/20 11:30 PM, Christian Borntraeger wrote: > > > > > > On 13.11.20 23:52, Randy Dunlap wrote: > >> Building on arch/s390/ flags this as an error, so add the > >> __noreturn attribute modifier to prevent the build error. > >> > >> cc1: some warnings being treated as errors > >> ../drivers/md/dm-writecache.c: In function 'persistent_memory_claim': > >> ../drivers/md/dm-writecache.c:323:1: error: no return statement in function returning non-void [-Werror=return-type] > > > > ok with me, but I am asking why > > > > the unreachable macro is not good enough. For x86 it obviously is. > > > > form arch/s390/include/asm/bug.h > > #define BUG() do { \ > > __EMIT_BUG(0); \ > > unreachable(); \ > > } while (0) > > > > Hi Christian, > > Good question. > I don't see any guidance about when to use one or the other etc. > > I see __noreturn being used 109 times and unreachable(); > being used 33 times, but only now that I look at them. > That had nothing to do with why I used __noreturn in the patch.
But doesn't that speak to the proper fix being needed in unreachable()? Or at a minimum the fix is needed to arch/s390/include/asm/bug.h's BUG.
I really don't think we should be papering over that by sprinkling __noreturn around the kernel's BUG() callers.
Maybe switch arch/s390/include/asm/bug.h's BUG to be like arch/mips/include/asm/bug.h? It itself uses __noreturn with a 'static inline' function definition rather than #define.
Does that fix the issue?
Thanks, Mike
p.s. you modified dm-writecache.c (not dm-writeback, wich doesn't exist).
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