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Message-ID: <51f1c4d7-6bc5-4ee8-bd6a-1a71b2dd5d5b@linux.intel.com> Date: Thu, 16 Nov 2023 13:59:52 +0800 From: "Abdul Rahim, Faizal" <faizal.abdul.rahim@...ux.intel.com> To: Simon Horman <horms@...nel.org> Cc: Vladimir Oltean <vladimir.oltean@....com>, Vinicius Costa Gomes <vinicius.gomes@...el.com>, Jamal Hadi Salim <jhs@...atatu.com>, Cong Wang <xiyou.wangcong@...il.com>, Jiri Pirko <jiri@...nulli.us>, "David S . Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v2 net 1/7] net/sched: taprio: fix too early schedules switching On 12/11/2023 6:31 pm, Simon Horman wrote: > On Tue, Nov 07, 2023 at 06:20:17AM -0500, Faizal Rahim wrote: >> In the current taprio code for dynamic schedule change, >> admin/oper schedule switching happens immediately when >> should_change_schedules() is true. Then the last entry of >> the old admin schedule stops being valid anymore from >> taprio_dequeue_from_txq’s perspective. >> >> To solve this, we have to delay the switch_schedules() call via >> the new cycle_time_correction variable. The variable serves 2 >> purposes: >> 1. Upon entering advance_sched(), if the value is set to a >> non-initialized value, it indicates that we need to change >> schedule. >> 2. Store the cycle time correction value which will be used for >> negative or positive correction. >> >> Fixes: a3d43c0d56f1 ("taprio: Add support adding an admin schedule") >> Signed-off-by: Faizal Rahim <faizal.abdul.rahim@...ux.intel.com> >> --- >> net/sched/sch_taprio.c | 9 +++++++-- >> 1 file changed, 7 insertions(+), 2 deletions(-) >> >> diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c >> index 2e1949de4171..dee103647823 100644 >> --- a/net/sched/sch_taprio.c >> +++ b/net/sched/sch_taprio.c >> @@ -41,6 +41,7 @@ static struct static_key_false taprio_have_working_mqprio; >> #define TXTIME_ASSIST_IS_ENABLED(flags) ((flags) & TCA_TAPRIO_ATTR_FLAG_TXTIME_ASSIST) >> #define FULL_OFFLOAD_IS_ENABLED(flags) ((flags) & TCA_TAPRIO_ATTR_FLAG_FULL_OFFLOAD) >> #define TAPRIO_FLAGS_INVALID U32_MAX >> +#define INIT_CYCLE_TIME_CORRECTION S64_MIN >> >> struct sched_entry { >> /* Durations between this GCL entry and the GCL entry where the >> @@ -75,6 +76,7 @@ struct sched_gate_list { >> ktime_t cycle_end_time; >> s64 cycle_time; >> s64 cycle_time_extension; >> + s64 cycle_time_correction; >> s64 base_time; >> }; >> >> @@ -940,8 +942,10 @@ static enum hrtimer_restart advance_sched(struct hrtimer *timer) >> admin = rcu_dereference_protected(q->admin_sched, >> lockdep_is_held(&q->current_entry_lock)); >> >> - if (!oper) >> + if (!oper || oper->cycle_time_correction != INIT_CYCLE_TIME_CORRECTION) { > > Hi Faizal, > > The first condition above expects that oper may be NULL, but the line below > dereferences it unconditionally. This doesn't seem correct, one way or the > other. > Thanks for pointing this out, sorry for this blunder. Will update. > As flagged by Smatch and Coccinelle. > >> + oper->cycle_time_correction = INIT_CYCLE_TIME_CORRECTION; >> switch_schedules(q, &admin, &oper); >> + } >> >> /* This can happen in two cases: 1. this is the very first run >> * of this function (i.e. we weren't running any schedule > > ... >
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