taprio: Fix still allowing changing the flags during runtime
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: 60750333c176 ("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>
projects / kernel.git / commit