On Fri, Jun 19, 2020 at 8:14 PM Kees Cook <keesc...@chromium.org> wrote:
>
> On Wed, Jun 10, 2020 at 10:34:16AM -0000, tip-bot2 for Peter Zijlstra wrote:
> > The following commit has been merged into the sched/urgent branch of tip:
> >
> > Commit-ID: bfb9fbe0f7e70ec5c8e51ee55b6968d4dff14456
> > Gitweb:
> > https://git.kernel.org/tip/bfb9fbe0f7e70ec5c8e51ee55b6968d4dff14456
> > Author: Peter Zijlstra <pet...@infradead.org>
> > AuthorDate: Wed, 10 Jun 2020 12:14:09 +02:00
> > Committer: Peter Zijlstra <pet...@infradead.org>
> > CommitterDate: Wed, 10 Jun 2020 12:30:19 +02:00
> >
> > sched: Fix RANDSTRUCT build fail
> >
> > As a temporary build fix, the proper cleanup needs more work.
> >
> > Reported-by: Guenter Roeck <li...@roeck-us.net>
> > Reported-by: Eric Biggers <ebigg...@kernel.org>
> > Suggested-by: Eric Biggers <ebigg...@kernel.org>
> > Suggested-by: Kees Cook <keesc...@chromium.org>
> > Fixes: a148866489fb ("sched: Replace rq::wake_list")
> > Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
>
> Hi, can this please get sent to Linus before -rc2? With a148866489fb in
> -rc1, all the CI with the GCC plugins installed have been failing their
> all*config builds. This entered -next 9 days ago (and fixed the -next
> builds), but Linus's tree is still failing:
Ugh.
I actually think the problem goes deeper than that.
The code expects the list entries to be of type 'call_single_data_t'
Then they damn well should be that type.
Note how "call_single_data_t" also implies certain alignment rules
that the hack in 'struct task_struct' does *not* have, and while that
doesn't matter on x86, it could matter on other architectures.
So no, I don't think Peter's patch is correct. It may make the build
pass, but that "check the offsets between two fields" is not
sufficient.
Now, if we could create a new
struct __call_single_list_entry {
struct llist_node llist;
unsigned int flags;
} call_single_list_entry_t;
and use that as part of thecall_single_data_t and only use that for
tyhe traversal of the list, then that would avoid the alignment issue
and the waste of space in struct task_struct.
Hmm?
Peter/Ingo?
Linus
