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SubjectRe: [PATCH] rcu/tree: Force quiescent state on callback overload
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Hi Paul,

On 6/22/2020 1:20 AM, Paul E. McKenney wrote:
> On Mon, Jun 22, 2020 at 12:07:27AM +0530, Neeraj Upadhyay wrote:
>> On callback overload, we want to force quiescent state immediately,
>> for the first and second fqs. Enforce the same, by including
>> RCU_GP_FLAG_OVLD flag, in fqsstart check.
>>
>> Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
>
> Good catch!
>
> But what did you do to verify that this change does the right thing?
>
> Thanx, Paul
>

I haven't done a runtime verification of this code path; I posted this,
based on review of this code.


Thanks
Neeraj

>> ---
>> 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 d0988a1..6226bfb 100644
>> --- a/kernel/rcu/tree.c
>> +++ b/kernel/rcu/tree.c
>> @@ -1865,7 +1865,7 @@ static void rcu_gp_fqs_loop(void)
>> break;
>> /* If time for quiescent-state forcing, do it. */
>> if (!time_after(rcu_state.jiffies_force_qs, jiffies) ||
>> - (gf & RCU_GP_FLAG_FQS)) {
>> + (gf & (RCU_GP_FLAG_FQS | RCU_GP_FLAG_OVLD))) {
>> trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
>> TPS("fqsstart"));
>> rcu_gp_fqs(first_gp_fqs);
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
>> a Linux Foundation Collaborative Project
>>

--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member of the Code Aurora Forum, hosted by The Linux Foundation

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