| Message ID | alpine.LFD.2.20.1612140949190.1657@knanqh.ubzr |
|---|---|
| State | New |
| Headers | show |
Hello, On Wed, Dec 14, 2016 at 10:14:39AM -0500, Nicolas Pitre wrote: > On Wed, 14 Dec 2016, Guenter Roeck wrote: > > > avr32:allnoconfig: > > > > kernel/built-in.o: In function `do_adjtimex': > > (.text+0x1d748): undefined reference to `posix_timer_event' > > make[1]: *** [vmlinux] Error 1 > > > > metag:allnoconfig: > > > > kernel/built-in.o: In function `alarm_handle_timer': > > alarmtimer.c:(.text.alarm_handle_timer+0x38): undefined reference to > > `posix_timer_event' > > > > openrisc:allnoconfig: > > > > kernel/built-in.o: In function `alarm_handle_timer': > > alarmtimer.c:(.text+0x3fca4): undefined reference to `posix_timer_event' > > > > unicore32:allnoconfig: > > > > kernel/built-in.o: In function `alarm_handle_timer': > > memremap.c:(.text+0x31c1c): undefined reference to `posix_timer_event' > > > > Since I don't run allnoconfig builds for all architectures, I strongly suspect > > that more are affected. > > This is a known problem. Oddly enough only those "less popular" > architectures are affected. > > > Looking into alarmtimer.c, with seems to call posix_timer_event() > > unconditionally, I don't entirely understand how this can work in the > > first place. Maybe I am missing something, though. > > The magic is in alarmtimer_init(): > > if (IS_ENABLED(CONFIG_POSIX_TIMERS)) { > posix_timers_register_clock(CLOCK_REALTIME_ALARM, &alarm_clock); > posix_timers_register_clock(CLOCK_BOOTTIME_ALARM, &alarm_clock); > } > > If CONFIG_POSIX_TIMERS is not enabled, the condition becomes a constant > zero. The posix_timers_register_clock calls are then optimized away by > the compiler. In turn the alarm_clock structure has no longer any > reference to it and therefore is also optimized away, including its > method functions such as alarm_timer_create() and finally > alarm_handle_timer(). > > But for some reasons, some gcc versions (mainly for "secondary" > architectures) fail to optimize away all that code, and a dead reference > to posix_timer_event() remains in the compiled code. > > There is a fix already queued in the mm tree. It goes like this: > > posix-timers: give lazy compilers some help optimizing code away > > The OpenRISC compiler (so far) fails to optimize away a large portion > of code containing a reference to posix_timer_event in alarmtimer.c when > CONFIG_POSIX_TIMERS is unset. Let's give it a direct clue to let the build > succeed. To be fair, this might be related to compiler version only. I guess its not an excuse, but when i compile with or1k-elf-gcc (version 5.3.0) I dont get this issue. I guess other archs are not breaking because they are being tested is a newer compiler? Tested will allnoconfig Compiler version: Using built-in specs. COLLECT_GCC=or1k-elf-gcc COLLECT_LTO_WRAPPER=/opt/shorne/software/or1k/libexec/gcc/or1k-elf/5.3.0/lto-wrapper Target: or1k-elf Configured with: ../or1k-gcc/configure --target=or1k-elf --prefix=/opt/shorne/software/or1k --enable-languages=c,c++ --disable-shared --disable-libssp --with-newlib Thread model: single gcc version 5.3.0 (GCC) -Stafford > This fixes > [linux-next:master 6682/7183] alarmtimer.c:undefined reference to `posix_timer_event' > reported by kbuild test robot. > > Signed-off-by: Nicolas Pitre <nico@linaro.org> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Josh Triplett <josh@joshtriplett.org> > Signed-off-by: Andrew Morton <akpm@linux-foundation.org> > > diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c > index 9b08ca391a..3921cf7fea 100644 > --- a/kernel/time/alarmtimer.c > +++ b/kernel/time/alarmtimer.c > @@ -516,7 +516,8 @@ static enum alarmtimer_restart alarm_handle_timer(struct alarm *alarm, > > spin_lock_irqsave(&ptr->it_lock, flags); > if ((ptr->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE) { > - if (posix_timer_event(ptr, 0) != 0) > + if (IS_ENABLED(CONFIG_POSIX_TIMERS) && > + posix_timer_event(ptr, 0) != 0) > ptr->it_overrun++; > } >
diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c index 9b08ca391a..3921cf7fea 100644 --- a/kernel/time/alarmtimer.c +++ b/kernel/time/alarmtimer.c @@ -516,7 +516,8 @@ static enum alarmtimer_restart alarm_handle_timer(struct alarm *alarm, spin_lock_irqsave(&ptr->it_lock, flags); if ((ptr->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE) { - if (posix_timer_event(ptr, 0) != 0) + if (IS_ENABLED(CONFIG_POSIX_TIMERS) && + posix_timer_event(ptr, 0) != 0) ptr->it_overrun++; }