Hi Arnd,
On 10/07/2019 14:01, Arnd Bergmann wrote:
On 32-bit x86 when building with clang-9, the loop gets turned back into an inefficient division that causes a link error:
kernel/time/vsyscall.o: In function `update_vsyscall': vsyscall.c:(.text+0xe3): undefined reference to `__udivdi3'
Use the provided __iter_div_u64_rem() function that is meant to address the same case in other files.
Fixes: 44f57d788e7d ("timekeeping: Provide a generic update_vsyscall() implementation") Signed-off-by: Arnd Bergmann arnd@arndb.de
kernel/time/vsyscall.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/kernel/time/vsyscall.c b/kernel/time/vsyscall.c index a80893180826..8cf3596a4ce6 100644 --- a/kernel/time/vsyscall.c +++ b/kernel/time/vsyscall.c @@ -104,11 +104,7 @@ void update_vsyscall(struct timekeeper *tk) vdso_ts->sec = tk->xtime_sec + tk->wall_to_monotonic.tv_sec; nsec = tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift; nsec = nsec + tk->wall_to_monotonic.tv_nsec;
- while (nsec >= NSEC_PER_SEC) {
nsec = nsec - NSEC_PER_SEC;vdso_ts->sec++;- }
- vdso_ts->nsec = nsec;
- vdso_ts->sec += __iter_div_u64_rem(nsec, NSEC_PER_SEC, &vdso_ts->nsec);
if (__arch_use_vsyscall(vdata)) update_vdso_data(vdata, tk);
I am trying to test this patch using clang-9 tip:
# clang -v clang version 9.0.0 (git@github.com:llvm-mirror/clang.git 6ed0749151866894a67a3e7eefdc1f3a547daa0e) (git@github.com:llvm-mirror/llvm.git a10a70238ace1093cad3adeb94814b422bd1b5c1)
but I get a lot of errors similar to the one below:
In file included from ~/linux/arch/x86/events/amd/core.c:11: ~/linux/arch/x86/events/amd/../perf_event.h:824:21: error: invalid output size for constraint '=q' u64 disable_mask = __this_cpu_read(cpu_hw_events.perf_ctr_virt_mask); ^ ~/linux/include/linux/percpu-defs.h:447:2: note: expanded from macro '__this_cpu_read' raw_cpu_read(pcp); \ ^ ~/linux/include/linux/percpu-defs.h:421:28: note: expanded from macro 'raw_cpu_read' #define raw_cpu_read(pcp) __pcpu_size_call_return(raw_cpu_read_, pcp) ^ ~/linux/include/linux/percpu-defs.h:322:23: note: expanded from macro '__pcpu_size_call_return' case 1: pscr_ret__ = stem##1(variable); break; \ ^ <scratch space>:110:1: note: expanded from here raw_cpu_read_1 ^ ~/linux/arch/x86/include/asm/percpu.h:394:30: note: expanded from macro 'raw_cpu_read_1' #define raw_cpu_read_1(pcp) percpu_from_op(, "mov", pcp) ^ ~/linux/arch/x86/include/asm/percpu.h:189:15: note: expanded from macro 'percpu_from_op' : "=q" (pfo_ret__) \
Could you please tell me which version of the compiler did you use?
My building command is:
# make mrproper && make CC=clang HOSTCC=clang i386_defconfig && make ARCH=i386 CC=clang HOSTCC=clang -j56