On 03/02/2017 04:42 PM, Steven Rostedt wrote: > On Thu, 2 Mar 2017 16:07:19 -0500 > Jason Baron <jba...@akamai.com> wrote: > >> On 02/28/2017 11:32 AM, Boris Ostrovsky wrote: >>> Pre-4.6 gcc do not allow direct static initialization of members of >>> anonymous structs/unions. After commit 3821fd35b58d ("jump_label: >>> Reduce the size of struct static_key") STATIC_KEY_INIT_{TRUE|FALSE} >>> definitions cannot be compiled with those older compilers. >>> >>> Placing initializers inside curved brackets works around this problem. >>> >>> Signed-off-by: Boris Ostrovsky <boris.ostrov...@oracle.com> >>> --- >>> include/linux/jump_label.h | 4 ++-- >>> 1 file changed, 2 insertions(+), 2 deletions(-) >>> >>> diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h >>> index 8e06d75..518020b 100644 >>> --- a/include/linux/jump_label.h >>> +++ b/include/linux/jump_label.h >>> @@ -166,10 +166,10 @@ extern void arch_jump_label_transform_static(struct >>> jump_entry *entry, >>> */ >>> #define STATIC_KEY_INIT_TRUE \ >>> { .enabled = { 1 }, \ >>> - .entries = (void *)JUMP_TYPE_TRUE } >>> + { .entries = (void *)JUMP_TYPE_TRUE } } >>> #define STATIC_KEY_INIT_FALSE \ >>> { .enabled = { 0 }, \ >>> - .entries = (void *)JUMP_TYPE_FALSE } >>> + { .entries = (void *)JUMP_TYPE_FALSE } } >>> >>> #else /* !HAVE_JUMP_LABEL */ >>> >>> >> (Adding Steve to 'cc) >> >> Thanks for the fix. >> >> Reviewed-by: Jason Baron <jba...@akamai.com> > Funny, Chris pinged me on IRC telling me that jump labels broke with my > latest tree. And we discovered it was because of anonymous unions and > he was using an older compiler (4.4 or something). I didn't know how to > make it work, and we were just going to say "tough, jump labels are not > for 4.4". Although, didn't goto asm get added into 4.5? Did someone > backport it to the gcc 4.4 compilers? I believe 4.5 handles anonymous > unions.
Per https://gcc.gnu.org/bugzilla/show_bug.cgi?id=10676 this was fixed in 4.6. I don't know whether this was ever backported but my gcc 4.4.4 is definitely not able to deal with those initializers. As for the fix, it was , in fact, suggested to me by Linus at some point in the past when a similar issue came up. The only thing here is that we need to be careful about initialization order. -boris