Le 11/04/2024 à 10:12, Christophe Leroy a écrit : > > > Le 11/04/2024 à 09:16, Adrian Hunter a écrit : >> On 11/04/24 10:04, Arnd Bergmann wrote: >>> On Wed, Apr 10, 2024, at 17:32, Adrian Hunter wrote: >>>> BUG() does not return, and arch implementations of BUG() use >>>> unreachable() >>>> or other non-returning code. However with !CONFIG_BUG, the default >>>> implementation is often used instead, and that does not do that. x86 >>>> always >>>> uses its own implementation, but powerpc with !CONFIG_BUG gives a build >>>> error: >>>> >>>> kernel/time/timekeeping.c: In function ‘timekeeping_debug_get_ns’: >>>> kernel/time/timekeeping.c:286:1: error: no return statement in >>>> function >>>> returning non-void [-Werror=return-type] >>>> >>>> Add unreachable() to default !CONFIG_BUG BUG() implementation. >>> >>> I'm a bit worried about this patch, since we have had problems >>> with unreachable() inside of BUG() in the past, and as far as I >>> can remember, the current version was the only one that >>> actually did the right thing on all compilers. >>> >>> One problem with an unreachable() annotation here is that if >>> a compiler misanalyses the endless loop, it can decide to >>> throw out the entire code path leading up to it and just >>> run into undefined behavior instead of printing a BUG() >>> message. >>> >>> Do you know which compiler version show the warning above? >> >> Original report has a list >> >> https://lore.kernel.org/all/CA+G9fYvjdZCW=7ZGxS6A_3bysjQ56YF7S-+PNLQ_8a4DKh1Bhg@xxxxxxxxxxxxxx/ >> > > Looking at the report, I think the correct fix should be to use > BUILD_BUG() instead of BUG() I confirm the error goes away with the following change to next-20240411 on powerpc tinyconfig with gcc 13.2 diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 4e18db1819f8..3d5ac0cdd721 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -282,7 +282,7 @@ static inline void timekeeping_check_update(struct timekeeper *tk, u64 offset) } static inline u64 timekeeping_debug_get_ns(const struct tk_read_base *tkr) { - BUG(); + BUILD_BUG(); } #endif
