On 14/12/16 14:42, Boqun Feng wrote: > 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 ;-)
Yep, that's totally fine. Thanks.
Colin
>
> 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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