[PATCH 2/2] sched/deadline: fix races between rt_mutex_setprio and dl_task_timer

From: Juri Lelli
Date: Thu Oct 09 2014 - 06:36:55 EST

Signed-off-by: Juri Lelli <juri.lelli@xxxxxxx>
---
kernel/sched/deadline.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index e89c27b..16a10f0 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -518,12 +518,20 @@ again:
}

/*
- * We need to take care of a possible races here. In fact, the
- * task might have changed its scheduling policy to something
- * different from SCHED_DEADLINE or changed its reservation
- * parameters (through sched_setattr()).
+ * We need to take care of several possible races here:
+ *
+ * - the task might have changed its scheduling policy
+ * to something different than SCHED_DEADLINE
+ * - the task might have changed its reservation parameters
+ * (through sched_setattr())
+ * - the task might have been boosted by someone else and
+ * might be in the boosting/deboosting path
+ *
+ * In all this cases we bail out, has the task is already
+ * in the runqueue or is going to be enqueued back anyway.
*/
- if (!dl_task(p) || dl_se->dl_new)
+ if (!dl_task(p) || dl_se->dl_new ||
+ dl_se->dl_boosted || !dl_se->dl_throttled)
goto unlock;

sched_clock_tick();
--
2.1.0

> runnable tasks:
> task PID tree-key switches prio exec-runtime sum-exec sum-sleep
> ----------------------------------------------------------------------------------------------------------
> systemd 1 170.771190 2147 120 170.771190 433.550134 359375.395748 /autogroup-1
> kthreadd 2 12481.085697 66 120 12481.085697 1.062411 848978.893057 /
> ksoftirqd/0 3 12486.586001 10125 120 12486.586001 48.522819 856220.673708 /
> kworker/0:0H 5 1218.349308 6 100 1218.349308 0.106697 835.585066 /
> kworker/u2:0 6 12483.710138 1947 120 12483.710138 45.712779 854218.654119 /
> khelper 7 13.326326 2 100 13.326326 0.000000 0.000000 /
> kdevtmpfs 8 2001.861157 139 120 2001.861157 1.787992 10775.571085 /
> netns 9 17.326324 2 100 17.326324 0.000000 0.000000 /
> kworker/u2:1 10 2001.760377 678 120 2001.760377 9.362114 10766.675796 /
> writeback 19 32.293597 2 100 32.293597 0.003126 0.002243 /
> crypto 21 33.494501 2 100 33.494501 0.002662 0.002051 /
> bioset 23 34.995536 2 100 34.995536 0.002601 0.002002 /
> kblockd 25 36.497285 2 100 36.497285 0.003835 0.002050 /
> ata_sff 61 78.865458 2 100 78.865458 0.004438 0.002205 /
> khubd 64 80.079505 2 120 80.079505 0.015444 0.003833 /
> md 66 81.268188 2 100 81.268188 0.003050 0.002173 /
> kworker/0:1 68 12484.564192 957 120 12484.564192 49.238817 855345.418329 /
> cfg80211 69 82.636198 2 100 82.636198 0.003627 0.002132 /
> rpciod 130 156.580245 2 100 156.580245 0.005374 0.004012 /
> kswapd0 138 928.454330 3 120 928.454330 0.048229 99.749401 /
> fsnotify_mark 143 1963.891522 14 120 1963.891522 0.065959 3496.886517 /
> nfsiod 146 171.432785 2 100 171.432785 0.004305 0.003535 /
> xfsalloc 149 174.366108 2 100 174.366108 0.002861 0.002284 /
> xfs_mru_cache 151 175.567171 2 100 175.567171 0.002752 0.002090 /
> xfslogd 153 177.068445 2 100 177.068445 0.003142 0.002171 /
> acpi_thermal_pm 177 192.956400 2 100 192.956400 0.003639 0.002317 /
> scsi_eh_0 203 1188.912866 8 120 1188.912866 2.029062 153.702869 /
> scsi_tmf_0 205 223.187411 2 100 223.187411 0.003086 0.002421 /
> scsi_eh_1 207 1531.958332 29 120 1531.958332 2.988008 1276.298054 /
> scsi_tmf_1 209 226.190410 2 100 226.190410 0.004007 0.002328 /
> kpsmoused 218 235.418718 2 100 235.418718 0.003621 0.002384 /
> ipv6_addrconf 227 244.650047 2 100 244.650047 0.004004 0.004044 /
> deferwq 232 247.754373 2 100 247.754373 0.003005 0.002112 /
> kworker/0:1H 882 12482.321178 1873 100 12482.321178 51.220049 850000.764070 /
> xfs-data/sda2 887 1230.066143 2 100 1230.066143 0.003715 0.002886 /
> xfs-conv/sda2 888 1231.567109 2 100 1231.567109 0.002769 0.002330 /
> xfs-cil/sda2 889 1233.568672 2 100 1233.568672 0.044412 0.002514 /
> xfsaild/sda2 890 12484.343046 4544 120 12484.343046 74.991234 847492.165181 /
> systemd-journal 902 1019.896708 410 120 1019.896708 1021.188821 848668.196674 /autogroup-5
> kauditd 905 7231.521873 59 120 7231.521873 0.606636 358980.677314 /
> systemd-udevd 971 60.572337 520 120 60.572337 53.544845 12283.357288 /autogroup-10
> jbd2/sda1-8 1422 1957.029513 2 120 1957.029513 0.062018 0.004464 /
> ext4-rsv-conver 1423 1959.032062 2 100 1959.032062 0.004310 0.002700 /
> auditd 1428 6.142863 98 116 6.142863 10.602551 845312.563408 /autogroup-21
> auditd 1436 5.502422 81 116 5.502422 2.335235 357502.433148 /autogroup-21
> NetworkManager 1445 82.669958 562 120 82.669958 64.904912 844091.171520 /autogroup-26
> NetworkManager 1467 20.709072 1 120 20.709072 0.014731 0.000000 /autogroup-26
> gmain 1470 66.064602 6 120 66.064602 0.366758 3699.249128 /autogroup-26
> gdbus 1474 79.637929 140 120 79.637929 4.511798 838151.788025 /autogroup-26
> systemd-logind 1446 8.311585 106 120 8.311585 9.677422 355305.433254 /autogroup-27
> dbus-daemon 1447 23.241715 345 120 23.241715 24.616880 844172.717523 /autogroup-28
> crond 1449 3.123550 18 120 3.123550 4.516948 841485.755390 /autogroup-29
> agetty 1455 2.936206 7 120 2.936206 7.052828 4305.395671 /autogroup-37
> agetty 1456 12.159459 11 120 12.159459 16.314073 3286.999222 /autogroup-36
> polkitd 1475 20.631235 93 120 20.631235 15.310572 349234.784825 /autogroup-32
> gmain 1478 8.881526 2 120 8.881526 0.065824 0.000000 /autogroup-32
> gdbus 1479 21.328501 38 120 21.328501 2.320225 349229.316491 /autogroup-32
> JS GC Helper 1480 14.370672 1 120 14.370672 0.031663 0.000000 /autogroup-32
> JS Sour~ Thread 1481 17.473336 7 120 17.473336 0.071963 3.840505 /autogroup-32
> runaway-killer- 1482 20.472425 5 120 20.472425 0.051006 0.250475 /autogroup-32
> sshd 1486 13.338015 67 120 13.338015 14.729391 349142.506840 /autogroup-35
> dhclient 1490 66.072235 65 120 66.072235 17.853255 1029.655591 /autogroup-26
> sshd 1505 27.497743 218 120 27.497743 25.950965 340666.314097 /autogroup-39
> systemd 1507 9.239660 26 120 9.239660 10.300048 729.175924 /autogroup-40
> bash 1508 4560.989053 99 120 4560.989053 14.807953 340582.911272 /autogroup-41
> (sd-pam) 1511 3.251482 1 120 3.251482 0.050250 0.000000 /autogroup-40
> kworker/0:0 1529 12482.288839 648 120 12482.288839 24.882158 535264.262021 /
> pthread_test 1536 0.000000 1510185 -1 0.000000 7142.137941 61496.639384 /autogroup-41
> pthread_test 1537 0.000000 1508994 -1 0.000000 19830.272655 0.000000 /autogroup-41
> sshd 1538 45.693223 859 120 45.693223 44.510292 497299.440632 /autogroup-42
> bash 1540 336.221438 292 120 336.221438 15.725550 496379.865890 /autogroup-43
> kworker/0:2 1561 12486.603821 72 120 12486.603821 1.009523 8366.740527 /
> R cat 1562 337.711978 0 120 337.711978 0.655400 0.000000 /autogroup-43
>
>
> [ 478.792528] pthread_test R running task 14232 1536 1508 0x10000080
> [ 478.793133] ffff880078d1bf60 0000000000000046 ffff88007caee5e0 ffff880078d1bfd8
> [ 478.793774] ffffffff81e1d4c0 00007fffa9c5e7b0 ffffffff8136187e 0000000000000000
> [ 478.794451] 00000000004009d0 00007fffa9c5e890 0000000000000000 0000000000000000
> [ 478.795118] Call Trace:
> [ 478.795326] [<ffffffff8136187e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
> [ 478.795846] [<ffffffff818b6d13>] schedule+0x23/0x60
> [ 478.796256] [<ffffffff818bd20f>] retint_careful+0x12/0x2d
> [ 478.796695] pthread_test S ffff88007caea8c0 14424 1537 1508 0x10000080
> [ 478.797287] ffff880078e63bd8 0000000000000046 ffff88007caea8c0 ffff880078e63fd8
> [ 478.797909] ffffffff81e1d4c0 ffff88007caea8c0 ffff880078e63be8 ffff880000158010
> [ 478.798542] ffff880078e63c58 0000000000000001 0000000000000001 ffff88007caea8c0
> [ 478.799175] Call Trace:
> [ 478.799376] [<ffffffff818b6d13>] schedule+0x23/0x60
> [ 478.799773] [<ffffffff818ba2fb>] __rt_mutex_slowlock+0x5b/0xe0
> [ 478.800257] [<ffffffff818ba4ce>] rt_mutex_slowlock+0xbe/0x1c0
> [ 478.800725] [<ffffffff8107cbea>] rt_mutex_timed_futex_lock+0x3a/0x40
> [ 478.801252] [<ffffffff810a6437>] futex_lock_pi.isra.20+0x257/0x370
> [ 478.801753] [<ffffffff81068cd5>] ? sched_clock_local.constprop.6+0x15/0x80
> [ 478.802317] [<ffffffff81068ec5>] ? sched_clock_cpu+0x55/0x80
> [ 478.802774] [<ffffffff81068f45>] ? local_clock+0x15/0x30
> [ 478.803225] [<ffffffff81068cd5>] ? sched_clock_local.constprop.6+0x15/0x80
> [ 478.803784] [<ffffffff810a720c>] do_futex+0x2bc/0xa90
> [ 478.804209] [<ffffffff81068cd5>] ? sched_clock_local.constprop.6+0x15/0x80
> [ 478.804766] [<ffffffff81068ec5>] ? sched_clock_cpu+0x55/0x80
> [ 478.805236] [<ffffffff81068f45>] ? local_clock+0x15/0x30
> [ 478.805669] [<ffffffff8109a936>] ? current_kernel_time+0x56/0xb0
> [ 478.806165] [<ffffffff8107648d>] ? trace_hardirqs_on+0xd/0x10
> [ 478.806629] [<ffffffff810a7a4c>] SyS_futex+0x6c/0x150
> [ 478.807046] [<ffffffff8100f60f>] ? syscall_trace_enter+0x21f/0x230
> [ 478.807549] [<ffffffff818bc75f>] tracesys+0xdc/0xe1
>
> (gdb) p $lx_task_by_pid(1536).dl
> $1 = {
> rb_node = {
> __rb_parent_color = 18446612134406055880,
> rb_right = 0x0,
> rb_left = 0x0
> },
> dl_runtime = 0,
> dl_deadline = 0,
> dl_period = 0,
> dl_bw = 0,
> runtime = -283620,
> deadline = 441965145261,
> flags = 0,
> dl_throttled = 0,
> dl_new = 0,
> dl_boosted = 1,
> dl_yielded = 0,
> dl_timer = {
> node = {
> node = {
> __rb_parent_color = 18446612134406055976,
> rb_right = 0x0,
> rb_left = 0x0
> },
> expires = {
> tv64 = 0
> }
> },
> _softexpires = {
> tv64 = 0
> },
> function = 0x0,
> base = 0xffffffff82010d68 <hrtimer_bases+136>,
> state = 0,
> start_pid = -1,
> start_site = 0x0,
> start_comm = '\000' <repeats 15 times>
> }
> }
>
> (gdb) p $lx_task_by_pid(1537).dl
> $2 = {
> rb_node = {
> __rb_parent_color = 18446612134406040232,
> rb_right = 0x0,
> rb_left = 0x0
> },
> dl_runtime = 100000,
> dl_deadline = 200000,
> dl_period = 200000,
> dl_bw = 524288,
> runtime = 70824,
> deadline = 441965047345,
> flags = 0,
> dl_throttled = 0,
> dl_new = 0,
> dl_boosted = 0,
> dl_yielded = 0,
> dl_timer = {
> node = {
> node = {
> __rb_parent_color = 18446612134406040328,
> rb_right = 0x0,
> rb_left = 0x0
> },
> expires = {
> tv64 = 441824359503
> }
> },
> _softexpires = {
> tv64 = 441824359503
> },
> function = 0xffffffff8106ce50 <dl_task_timer>,
> base = 0xffffffff82010d68 <hrtimer_bases+136>,
> state = 0,
> start_pid = 1537,
> start_site = 0xffffffff8106d178 <update_curr_dl+552>,
> start_comm = "pthread_test\000\000\000"
> }
> }
>
> cheers,
> daniel
>

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