From: Vinicius Costa Gomes vinicius.gomes@intel.com
[ Upstream commit a9d6227436f32142209f4428f2dc616761485112 ]
Because 'q->flags' starts as zero, and zero is a valid value, we aren't able to detect the transition from zero to something else during "runtime".
The solution is to initialize 'q->flags' with an invalid value, so we can detect if 'q->flags' was set by the user or not.
To better solidify the behavior, 'flags' handling is moved to a separate function. The behavior is: - 'flags' if unspecified by the user, is assumed to be zero; - 'flags' cannot change during "runtime" (i.e. a change() request cannot modify it);
With this new function we can remove taprio_flags, which should reduce the risk of future accidents.
Allowing flags to be changed was causing the following RCU stall:
[ 1730.558249] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: [ 1730.558258] rcu: 6-...0: (190 ticks this GP) idle=922/0/0x1 softirq=25580/25582 fqs=16250 [ 1730.558264] (detected by 2, t=65002 jiffies, g=33017, q=81) [ 1730.558269] Sending NMI from CPU 2 to CPUs 6: [ 1730.559277] NMI backtrace for cpu 6 [ 1730.559277] CPU: 6 PID: 0 Comm: swapper/6 Tainted: G E 5.5.0-rc6+ #35 [ 1730.559278] Hardware name: Gigabyte Technology Co., Ltd. Z390 AORUS ULTRA/Z390 AORUS ULTRA-CF, BIOS F7 03/14/2019 [ 1730.559278] RIP: 0010:__hrtimer_run_queues+0xe2/0x440 [ 1730.559278] Code: 48 8b 43 28 4c 89 ff 48 8b 75 c0 48 89 45 c8 e8 f4 bb 7c 00 0f 1f 44 00 00 65 8b 05 40 31 f0 68 89 c0 48 0f a3 05 3e 5c 25 01 <0f> 82 fc 01 00 00 48 8b 45 c8 48 89 df ff d0 89 45 c8 0f 1f 44 00 [ 1730.559279] RSP: 0018:ffff9970802d8f10 EFLAGS: 00000083 [ 1730.559279] RAX: 0000000000000006 RBX: ffff8b31645bff38 RCX: 0000000000000000 [ 1730.559280] RDX: 0000000000000000 RSI: ffffffff9710f2ec RDI: ffffffff978daf0e [ 1730.559280] RBP: ffff9970802d8f68 R08: 0000000000000000 R09: 0000000000000000 [ 1730.559280] R10: 0000018336d7944e R11: 0000000000000001 R12: ffff8b316e39f9c0 [ 1730.559281] R13: ffff8b316e39f940 R14: ffff8b316e39f998 R15: ffff8b316e39f7c0 [ 1730.559281] FS: 0000000000000000(0000) GS:ffff8b316e380000(0000) knlGS:0000000000000000 [ 1730.559281] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1730.559281] CR2: 00007f1105303760 CR3: 0000000227210005 CR4: 00000000003606e0 [ 1730.559282] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 1730.559282] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 1730.559282] Call Trace: [ 1730.559282] <IRQ> [ 1730.559283] ? taprio_dequeue_soft+0x2d0/0x2d0 [sch_taprio] [ 1730.559283] hrtimer_interrupt+0x104/0x220 [ 1730.559283] ? irqtime_account_irq+0x34/0xa0 [ 1730.559283] smp_apic_timer_interrupt+0x6d/0x230 [ 1730.559284] apic_timer_interrupt+0xf/0x20 [ 1730.559284] </IRQ> [ 1730.559284] RIP: 0010:cpu_idle_poll+0x35/0x1a0 [ 1730.559285] Code: 88 82 ff 65 44 8b 25 12 7d 73 68 0f 1f 44 00 00 e8 90 c3 89 ff fb 65 48 8b 1c 25 c0 7e 01 00 48 8b 03 a8 08 74 0b eb 1c f3 90 <48> 8b 03 a8 08 75 13 8b 05 be a8 a8 00 85 c0 75 ed e8 75 48 84 ff [ 1730.559285] RSP: 0018:ffff997080137ea8 EFLAGS: 00000202 ORIG_RAX: ffffffffffffff13 [ 1730.559285] RAX: 0000000000000001 RBX: ffff8b316bc3c580 RCX: 0000000000000000 [ 1730.559286] RDX: 0000000000000001 RSI: 000000002819aad9 RDI: ffffffff978da730 [ 1730.559286] RBP: ffff997080137ec0 R08: 0000018324a6d387 R09: 0000000000000000 [ 1730.559286] R10: 0000000000000400 R11: 0000000000000001 R12: 0000000000000006 [ 1730.559286] R13: ffff8b316bc3c580 R14: 0000000000000000 R15: 0000000000000000 [ 1730.559287] ? cpu_idle_poll+0x20/0x1a0 [ 1730.559287] ? cpu_idle_poll+0x20/0x1a0 [ 1730.559287] do_idle+0x4d/0x1f0 [ 1730.559287] ? complete+0x44/0x50 [ 1730.559288] cpu_startup_entry+0x1b/0x20 [ 1730.559288] start_secondary+0x142/0x180 [ 1730.559288] secondary_startup_64+0xb6/0xc0 [ 1776.686313] nvme nvme0: I/O 96 QID 1 timeout, completion polled
Fixes: 4cfd5779bd6e ("taprio: Add support for txtime-assist mode") Signed-off-by: Vinicius Costa Gomes vinicius.gomes@intel.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/sched/sch_taprio.c | 61 ++++++++++++++++++++++++++++++++----------------- 1 file changed, 41 insertions(+), 20 deletions(-)
--- a/net/sched/sch_taprio.c +++ b/net/sched/sch_taprio.c @@ -31,6 +31,7 @@ static DEFINE_SPINLOCK(taprio_list_lock)
#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
struct sched_entry { struct list_head list; @@ -1367,6 +1368,33 @@ static int taprio_mqprio_cmp(const struc return 0; }
+/* The semantics of the 'flags' argument in relation to 'change()' + * requests, are interpreted following two rules (which are applied in + * this order): (1) an omitted 'flags' argument is interpreted as + * zero; (2) the 'flags' of a "running" taprio instance cannot be + * changed. + */ +static int taprio_new_flags(const struct nlattr *attr, u32 old, + struct netlink_ext_ack *extack) +{ + u32 new = 0; + + if (attr) + new = nla_get_u32(attr); + + if (old != TAPRIO_FLAGS_INVALID && old != new) { + NL_SET_ERR_MSG_MOD(extack, "Changing 'flags' of a running schedule is not supported"); + return -EOPNOTSUPP; + } + + if (!taprio_flags_valid(new)) { + NL_SET_ERR_MSG_MOD(extack, "Specified 'flags' are not valid"); + return -EINVAL; + } + + return new; +} + static int taprio_change(struct Qdisc *sch, struct nlattr *opt, struct netlink_ext_ack *extack) { @@ -1375,7 +1403,6 @@ static int taprio_change(struct Qdisc *s struct taprio_sched *q = qdisc_priv(sch); struct net_device *dev = qdisc_dev(sch); struct tc_mqprio_qopt *mqprio = NULL; - u32 taprio_flags = 0; unsigned long flags; ktime_t start; int i, err; @@ -1388,21 +1415,14 @@ static int taprio_change(struct Qdisc *s if (tb[TCA_TAPRIO_ATTR_PRIOMAP]) mqprio = nla_data(tb[TCA_TAPRIO_ATTR_PRIOMAP]);
- if (tb[TCA_TAPRIO_ATTR_FLAGS]) { - taprio_flags = nla_get_u32(tb[TCA_TAPRIO_ATTR_FLAGS]); - - if (q->flags != 0 && q->flags != taprio_flags) { - NL_SET_ERR_MSG_MOD(extack, "Changing 'flags' of a running schedule is not supported"); - return -EOPNOTSUPP; - } else if (!taprio_flags_valid(taprio_flags)) { - NL_SET_ERR_MSG_MOD(extack, "Specified 'flags' are not valid"); - return -EINVAL; - } + err = taprio_new_flags(tb[TCA_TAPRIO_ATTR_FLAGS], + q->flags, extack); + if (err < 0) + return err;
- q->flags = taprio_flags; - } + q->flags = err;
- err = taprio_parse_mqprio_opt(dev, mqprio, extack, taprio_flags); + err = taprio_parse_mqprio_opt(dev, mqprio, extack, q->flags); if (err < 0) return err;
@@ -1457,7 +1477,7 @@ static int taprio_change(struct Qdisc *s mqprio->prio_tc_map[i]); }
- if (FULL_OFFLOAD_IS_ENABLED(taprio_flags)) + if (FULL_OFFLOAD_IS_ENABLED(q->flags)) err = taprio_enable_offload(dev, mqprio, q, new_admin, extack); else err = taprio_disable_offload(dev, q, extack); @@ -1477,14 +1497,14 @@ static int taprio_change(struct Qdisc *s q->txtime_delay = nla_get_u32(tb[TCA_TAPRIO_ATTR_TXTIME_DELAY]); }
- if (!TXTIME_ASSIST_IS_ENABLED(taprio_flags) && - !FULL_OFFLOAD_IS_ENABLED(taprio_flags) && + if (!TXTIME_ASSIST_IS_ENABLED(q->flags) && + !FULL_OFFLOAD_IS_ENABLED(q->flags) && !hrtimer_active(&q->advance_timer)) { hrtimer_init(&q->advance_timer, q->clockid, HRTIMER_MODE_ABS); q->advance_timer.function = advance_sched; }
- if (FULL_OFFLOAD_IS_ENABLED(taprio_flags)) { + if (FULL_OFFLOAD_IS_ENABLED(q->flags)) { q->dequeue = taprio_dequeue_offload; q->peek = taprio_peek_offload; } else { @@ -1501,7 +1521,7 @@ static int taprio_change(struct Qdisc *s goto unlock; }
- if (TXTIME_ASSIST_IS_ENABLED(taprio_flags)) { + if (TXTIME_ASSIST_IS_ENABLED(q->flags)) { setup_txtime(q, new_admin, start);
if (!oper) { @@ -1528,7 +1548,7 @@ static int taprio_change(struct Qdisc *s
spin_unlock_irqrestore(&q->current_entry_lock, flags);
- if (FULL_OFFLOAD_IS_ENABLED(taprio_flags)) + if (FULL_OFFLOAD_IS_ENABLED(q->flags)) taprio_offload_config_changed(q); }
@@ -1597,6 +1617,7 @@ static int taprio_init(struct Qdisc *sch * and get the valid one on taprio_change(). */ q->clockid = -1; + q->flags = TAPRIO_FLAGS_INVALID;
spin_lock(&taprio_list_lock); list_add(&q->taprio_list, &taprio_list);