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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Vincent Guittot <vincent.guittot@linaro.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>, Ben Segall <bsegall@google.com>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH AUTOSEL 5.5 05/58] sched/fair: Prevent unlimited runtime on throttled group
Date: Sat, 22 Feb 2020 21:20:26 -0500	[thread overview]
Message-ID: <20200223022119.707-5-sashal@kernel.org> (raw)
In-Reply-To: <20200223022119.707-1-sashal@kernel.org>

From: Vincent Guittot <vincent.guittot@linaro.org>

[ Upstream commit 2a4b03ffc69f2dedc6388e9a6438b5f4c133a40d ]

When a running task is moved on a throttled task group and there is no
other task enqueued on the CPU, the task can keep running using 100% CPU
whatever the allocated bandwidth for the group and although its cfs rq is
throttled. Furthermore, the group entity of the cfs_rq and its parents are
not enqueued but only set as curr on their respective cfs_rqs.

We have the following sequence:

sched_move_task
  -dequeue_task: dequeue task and group_entities.
  -put_prev_task: put task and group entities.
  -sched_change_group: move task to new group.
  -enqueue_task: enqueue only task but not group entities because cfs_rq is
    throttled.
  -set_next_task : set task and group_entities as current sched_entity of
    their cfs_rq.

Another impact is that the root cfs_rq runnable_load_avg at root rq stays
null because the group_entities are not enqueued. This situation will stay
the same until an "external" event triggers a reschedule. Let trigger it
immediately instead.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Ben Segall <bsegall@google.com>
Link: https://lkml.kernel.org/r/1579011236-31256-1-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 kernel/sched/core.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 1f4f8e850cab7..4b6b916ec1be4 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7067,8 +7067,15 @@ void sched_move_task(struct task_struct *tsk)
 
 	if (queued)
 		enqueue_task(rq, tsk, queue_flags);
-	if (running)
+	if (running) {
 		set_next_task(rq, tsk);
+		/*
+		 * After changing group, the running task may have joined a
+		 * throttled one but it's still the running task. Trigger a
+		 * resched to make sure that task can still run.
+		 */
+		resched_curr(rq);
+	}
 
 	task_rq_unlock(rq, tsk, &rf);
 }
-- 
2.20.1


  parent reply	other threads:[~2020-02-23  2:37 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-23  2:20 [PATCH AUTOSEL 5.5 01/58] ipmi:ssif: Handle a possible NULL pointer reference Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 02/58] drm/msm: Set dma maximum segment size for mdss Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 03/58] sched/core: Don't skip remote tick for idle CPUs Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 04/58] timers/nohz: Update NOHZ load in remote tick Sasha Levin
2020-02-23  2:20 ` Sasha Levin [this message]
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 06/58] dax: pass NOWAIT flag to iomap_apply Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 07/58] mac80211: consider more elements in parsing CRC Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 08/58] cfg80211: check wiphy driver existence for drvinfo report Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 09/58] io_uring: flush overflowed CQ events in the io_uring_poll() Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 10/58] s390/zcrypt: fix card and queue total counter wrap Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 11/58] qmi_wwan: re-add DW5821e pre-production variant Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 12/58] qmi_wwan: unconditionally reject 2 ep interfaces Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 13/58] NFSv4: Fix races between open and dentry revalidation Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 14/58] perf/smmuv3: Use platform_get_irq_optional() for wired interrupt Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 15/58] arm/ftrace: Fix BE text poking Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 16/58] sched/psi: Fix OOB write when writing 0 bytes to PSI files Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 17/58] perf/x86/intel: Add Elkhart Lake support Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 18/58] perf/x86/cstate: Add Tremont support Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 19/58] perf/x86/msr: " Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 20/58] ceph: do not execute direct write in parallel if O_APPEND is specified Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 21/58] ARM: dts: sti: fixup sound frame-inversion for stihxxx-b2120.dtsi Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 22/58] drm/amd/display: Do not set optimized_require to false after plane disable Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 23/58] RDMA/siw: Remove unwanted WARN_ON in siw_cm_llp_data_ready() Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 24/58] drm/amd/display: Check engine is not NULL before acquiring Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 25/58] drm/amd/display: Limit minimum DPPCLK to 100MHz Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 26/58] drm/amd/display: Add initialitions for PLL2 clock source Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 27/58] amdgpu: Prevent build errors regarding soft/hard-float FP ABI tags Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 28/58] soc/tegra: fuse: Fix build with Tegra194 configuration Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 29/58] i40e: Fix the conditional for i40e_vc_validate_vqs_bitmaps Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 30/58] net: ena: fix potential crash when rxfh key is NULL Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 31/58] net: ena: fix uses of round_jiffies() Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 32/58] net: ena: add missing ethtool TX timestamping indication Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 33/58] net: ena: fix incorrect default RSS key Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 34/58] net: ena: rss: do not allocate key when not supported Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 35/58] net: ena: rss: fix failure to get indirection table Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 36/58] net: ena: rss: store hash function as values and not bits Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 37/58] net: ena: fix incorrectly saving queue numbers when setting RSS indirection table Sasha Levin
2020-02-23  2:20 ` [PATCH AUTOSEL 5.5 38/58] net: ena: fix corruption of dev_idx_to_host_tbl Sasha Levin
2020-02-23  2:21 ` [PATCH AUTOSEL 5.5 39/58] net: ena: ethtool: use correct value for crc32 hash Sasha Levin
2020-02-23  2:21 ` [PATCH AUTOSEL 5.5 40/58] net: ena: ena-com.c: prevent NULL pointer dereference Sasha Levin
2020-02-23  2:21 ` [PATCH AUTOSEL 5.5 41/58] enic: prevent waking up stopped tx queues over watchdog reset Sasha Levin
2020-02-23  2:21 ` [PATCH AUTOSEL 5.5 42/58] ice: Fix switch between FW and SW LLDP Sasha Levin
2020-02-23  2:21 ` [PATCH AUTOSEL 5.5 43/58] ice: Don't allow same value for Rx tail to be written twice Sasha Levin
2020-02-23  2:21 ` [PATCH AUTOSEL 5.5 44/58] ice: fix and consolidate logging of NVM/firmware version information Sasha Levin
2020-02-23  2:21 ` [PATCH AUTOSEL 5.5 45/58] ice: update Unit Load Status bitmask to check after reset Sasha Levin
2020-02-23  2:21 ` [PATCH AUTOSEL 5.5 46/58] ice: Use ice_pf_to_dev Sasha Levin
2020-02-23  2:21 ` [PATCH AUTOSEL 5.5 47/58] ice: Use correct netif error function Sasha Levin
2020-02-23  2:21 ` [PATCH AUTOSEL 5.5 48/58] io-wq: don't call kXalloc_node() with non-online node Sasha Levin
2020-02-23  2:21 ` [PATCH AUTOSEL 5.5 49/58] cifs: Fix mode output in debugging statements Sasha Levin
2020-02-23  2:21 ` [PATCH AUTOSEL 5.5 50/58] bcache: ignore pending signals when creating gc and allocator thread Sasha Levin
2020-02-23  2:21 ` [PATCH AUTOSEL 5.5 51/58] cfg80211: add missing policy for NL80211_ATTR_STATUS_CODE Sasha Levin
2020-02-23  2:21 ` [PATCH AUTOSEL 5.5 52/58] mac80211: fix wrong 160/80+80 MHz setting Sasha Levin
2020-02-23  2:21 ` [PATCH AUTOSEL 5.5 53/58] net: hns3: add management table after IMP reset Sasha Levin
2020-02-23  2:21 ` [PATCH AUTOSEL 5.5 54/58] net: hns3: fix VF bandwidth does not take effect in some case Sasha Levin
2020-02-23  2:21 ` [PATCH AUTOSEL 5.5 55/58] net: hns3: fix a copying IPv6 address error in hclge_fd_get_flow_tuples() Sasha Levin
2020-02-23  2:21 ` [PATCH AUTOSEL 5.5 56/58] nvme/tcp: fix bug on double requeue when send fails Sasha Levin
2020-02-23  2:21 ` [PATCH AUTOSEL 5.5 57/58] nvme: prevent warning triggered by nvme_stop_keep_alive Sasha Levin
2020-02-23  2:21 ` [PATCH AUTOSEL 5.5 58/58] nvme/pci: move cqe check after device shutdown Sasha Levin

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