On Tue, Dec 13, 2016 at 11:33:19AM +0000, Colin Ian King wrote: > On 13/12/16 11:21, Boqun Feng wrote: > > On Tue, Dec 13, 2016 at 10:56:46AM +0000, Colin King wrote: > >> From: Colin Ian King <[email protected]> > >> > >> mask and bit are unsigned longs, so if bit is 31 we end up sign > >> extending the 1 and mask ends up as 0xffffffff80000000. Fix this > >> by explicitly adding integer suffix UL ensure 1 is a unsigned long > >> rather than an signed int. > >> > > > > Right, you are, and the tool is ;-) > > > > If @bit is greater than 32, we even got an undefined behavior in C ;-( > > This is my careless mistake, thank you for finding it out and fix it! > > > >> Issue found with static analysis with CoverityScan, CID 1388564 > >> > >> Fixes: 8965c3ce4718754db ("rcu: Use leaf_node_for_each_mask_possible_cpu() > >> in force_qs_rnp()") > >> Signed-off-by: Colin Ian King <[email protected]> > > > > I think Paul only queued that for running tests and I have almost > > finished a v2. I will fold your fix in my patch and add your SoB along > > with mine, does that work for you? > > Sure, that's good with me. >
Colin, as I'm going to take Mark's suggestion and use
leaf_node_cpu_bit() instead. So I'm going to drop your SoB but keep a
commit message saying you spotted the problem at the first place. Hope
that works with you ;-)
Regards,
Boqun
> >
> > TBH, this situation is kinda new to me, so if anyone has any suggestion,
> > please let me know ;-)
> >
> > Regards,
> > Boqun
> >
> >> ---
> >> kernel/rcu/tree.c | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> >> index 10162ac..6ecedd8 100644
> >> --- a/kernel/rcu/tree.c
> >> +++ b/kernel/rcu/tree.c
> >> @@ -3051,7 +3051,7 @@ static void force_qs_rnp(struct rcu_state *rsp,
> >>
> >> leaf_node_for_each_mask_possible_cpu(rnp, rnp->qsmask, bit, cpu)
> >> if (f(per_cpu_ptr(rsp->rda, cpu), isidle, maxj))
> >> - mask |= 1 << bit;
> >> + mask |= 1UL << bit;
> >>
> >> if (mask != 0) {
> >> /* Idle/offline CPUs, report (releases rnp->lock. */
> >> --
> >> 2.10.2
> >>
>
>
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