Messages in this thread |  | | Subject | Re: [patch 2.6.19-rc6] Stop gcc 4.1.0 optimizing wait_hpet_tick away | From | Nicholas Miell <> | Date | Tue, 28 Nov 2006 19:08:25 -0800 |
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On Wed, 2006-11-29 at 13:22 +1100, Keith Owens wrote: > Compiling 2.6.19-rc6 with gcc version 4.1.0 (SUSE Linux), > wait_hpet_tick is optimized away to a never ending loop and the kernel > hangs on boot in timer setup. > > 0000001a <wait_hpet_tick>: > 1a: 55 push %ebp > 1b: 89 e5 mov %esp,%ebp > 1d: eb fe jmp 1d <wait_hpet_tick+0x3> > > This is not a problem with gcc 3.3.5. Adding barrier() calls to > wait_hpet_tick does not help, making the variables volatile does. > > Signed-off-by: Keith Owens <kaos@ocs.com.au> > > --- > arch/i386/kernel/time_hpet.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > Index: linux-2.6/arch/i386/kernel/time_hpet.c > =================================================================== > --- linux-2.6.orig/arch/i386/kernel/time_hpet.c > +++ linux-2.6/arch/i386/kernel/time_hpet.c > @@ -51,7 +51,7 @@ static void hpet_writel(unsigned long d, > */ > static void __devinit wait_hpet_tick(void) > { > - unsigned int start_cmp_val, end_cmp_val; > + unsigned volatile int start_cmp_val, end_cmp_val; > > start_cmp_val = hpet_readl(HPET_T0_CMP); > do {
When you examine the inlined functions involved, this looks an awful lot like http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22278
Perhaps SUSE should fix their gcc instead of working around compiler problems in the kernel?
-- Nicholas Miell <nmiell@comcast.net>
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