From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>,
Davidlohr Bueso <dave@stgolabs.net>,
Linus Torvalds <torvalds@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Waiman Long <longman@redhat.com>,
Will Deacon <will.deacon@arm.com>, Ingo Molnar <mingo@kernel.org>,
Sasha Levin <sashal@kernel.org>
Subject: [PATCH AUTOSEL 4.20 38/77] sched/wake_q: Fix wakeup ordering for wake_q
Date: Thu, 14 Feb 2019 21:08:16 -0500 [thread overview]
Message-ID: <20190215020855.176727-38-sashal@kernel.org> (raw)
In-Reply-To: <20190215020855.176727-1-sashal@kernel.org>
From: Peter Zijlstra <peterz@infradead.org>
[ Upstream commit 4c4e3731564c8945ac5ac90fc2a1e1f21cb79c92 ]
Notable cmpxchg() does not provide ordering when it fails, however
wake_q_add() requires ordering in this specific case too. Without this
it would be possible for the concurrent wakeup to not observe our
prior state.
Andrea Parri provided:
C wake_up_q-wake_q_add
{
int next = 0;
int y = 0;
}
P0(int *next, int *y)
{
int r0;
/* in wake_up_q() */
WRITE_ONCE(*next, 1); /* node->next = NULL */
smp_mb(); /* implied by wake_up_process() */
r0 = READ_ONCE(*y);
}
P1(int *next, int *y)
{
int r1;
/* in wake_q_add() */
WRITE_ONCE(*y, 1); /* wake_cond = true */
smp_mb__before_atomic();
r1 = cmpxchg_relaxed(next, 1, 2);
}
exists (0:r0=0 /\ 1:r1=0)
This "exists" clause cannot be satisfied according to the LKMM:
Test wake_up_q-wake_q_add Allowed
States 3
0:r0=0; 1:r1=1;
0:r0=1; 1:r1=0;
0:r0=1; 1:r1=1;
No
Witnesses
Positive: 0 Negative: 3
Condition exists (0:r0=0 /\ 1:r1=0)
Observation wake_up_q-wake_q_add Never 0 3
Reported-by: Yongji Xie <elohimes@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/sched/core.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 6fedf3a98581..463af32de32c 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -405,10 +405,11 @@ void wake_q_add(struct wake_q_head *head, struct task_struct *task)
* its already queued (either by us or someone else) and will get the
* wakeup due to that.
*
- * This cmpxchg() executes a full barrier, which pairs with the full
- * barrier executed by the wakeup in wake_up_q().
+ * In order to ensure that a pending wakeup will observe our pending
+ * state, even in the failed case, an explicit smp_mb() must be used.
*/
- if (cmpxchg(&node->next, NULL, WAKE_Q_TAIL))
+ smp_mb__before_atomic();
+ if (cmpxchg_relaxed(&node->next, NULL, WAKE_Q_TAIL))
return;
get_task_struct(task);
--
2.19.1
next prev parent reply other threads:[~2019-02-15 2:40 UTC|newest]
Thread overview: 92+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-15 2:07 [PATCH AUTOSEL 4.20 01/77] drm/msm: Unblock writer if reader closes file Sasha Levin
2019-02-15 2:07 ` [PATCH AUTOSEL 4.20 02/77] ASoC: Intel: Haswell/Broadwell: fix setting for .dynamic field Sasha Levin
2019-02-15 2:07 ` [PATCH AUTOSEL 4.20 03/77] ALSA: compress: prevent potential divide by zero bugs Sasha Levin
2019-02-15 2:07 ` [PATCH AUTOSEL 4.20 04/77] ASoC: rt5682: Fix recording no sound issue Sasha Levin
2019-02-15 2:07 ` [PATCH AUTOSEL 4.20 05/77] ASoC: Variable "val" in function rt274_i2c_probe() could be uninitialized Sasha Levin
2019-02-15 2:07 ` [PATCH AUTOSEL 4.20 06/77] ASoC: soc-core: defer card probe until all component is added to list Sasha Levin
2019-02-15 11:57 ` Mark Brown
2019-02-27 17:31 ` Sasha Levin
2019-02-15 2:07 ` [PATCH AUTOSEL 4.20 07/77] clk: tegra: dfll: Fix a potential Oop in remove() Sasha Levin
2019-02-15 2:07 ` [PATCH AUTOSEL 4.20 08/77] clk: sysfs: fix invalid JSON in clk_dump Sasha Levin
2019-02-15 2:07 ` [PATCH AUTOSEL 4.20 09/77] clk: vc5: Abort clock configuration without upstream clock Sasha Levin
2019-02-15 2:07 ` [PATCH AUTOSEL 4.20 10/77] ASoC: soc-core: Hold client_mutex around soc_init_dai_link() Sasha Levin
2019-02-15 11:57 ` Mark Brown
2019-02-27 17:31 ` Sasha Levin
2019-02-15 2:07 ` [PATCH AUTOSEL 4.20 11/77] thermal: int340x_thermal: Fix a NULL vs IS_ERR() check Sasha Levin
2019-02-15 2:07 ` [PATCH AUTOSEL 4.20 12/77] usb: dwc3: gadget: synchronize_irq dwc irq in suspend Sasha Levin
2019-02-15 2:07 ` [PATCH AUTOSEL 4.20 13/77] usb: dwc3: gadget: Fix the uninitialized link_state when udc starts Sasha Levin
2019-02-15 2:07 ` [PATCH AUTOSEL 4.20 14/77] usb: gadget: Potential NULL dereference on allocation error Sasha Levin
2019-02-15 2:07 ` [PATCH AUTOSEL 4.20 15/77] HID: i2c-hid: Disable runtime PM on Goodix touchpad Sasha Levin
2019-02-15 2:07 ` [PATCH AUTOSEL 4.20 16/77] ASoC: soc-core: fix init platform memory handling Sasha Levin
2019-02-15 11:58 ` Mark Brown
2019-02-27 17:34 ` Sasha Levin
2019-02-15 2:07 ` [PATCH AUTOSEL 4.20 17/77] ASoC: core: Make snd_soc_find_component() more robust Sasha Levin
2019-02-15 2:07 ` [PATCH AUTOSEL 4.20 18/77] selftests: rtc: rtctest: fix alarm tests Sasha Levin
2019-02-15 2:07 ` [PATCH AUTOSEL 4.20 19/77] selftests: rtc: rtctest: add alarm test on minute boundary Sasha Levin
2019-02-15 2:07 ` [PATCH AUTOSEL 4.20 20/77] genirq: Make sure the initial affinity is not empty Sasha Levin
2019-02-15 2:07 ` [PATCH AUTOSEL 4.20 21/77] x86/mm/mem_encrypt: Fix erroneous sizeof() Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 22/77] ASoC: core: Don't defer probe on optional, NULL components Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 23/77] ASoC: rt5682: Fix PLL source register definitions Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 24/77] ASoC: dapm: change snprintf to scnprintf for possible overflow Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 25/77] ASoC: imx-audmux: " Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 26/77] selftests/vm/gup_benchmark.c: match gup struct to kernel Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 27/77] phy: ath79-usb: Fix the power on error path Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 28/77] phy: ath79-usb: Fix the main reset name to match the DT binding Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 29/77] selftests: seccomp: use LDLIBS instead of LDFLAGS Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 30/77] selftests: gpio-mockup-chardev: Check asprintf() for error Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 31/77] irqchip/gic-v3-mbi: Fix uninitialized mbi_lock Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 32/77] ARC: fix __ffs return value to avoid build warnings Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 33/77] ARC: show_regs: lockdep: avoid page allocator Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 34/77] drivers: thermal: int340x_thermal: Fix sysfs race condition Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 35/77] staging: rtl8723bs: Fix build error with Clang when inlining is disabled Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 36/77] mac80211: fix miscounting of ttl-dropped frames Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 37/77] sched/wait: Fix rcuwait_wake_up() ordering Sasha Levin
2019-02-15 2:08 ` Sasha Levin [this message]
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 39/77] futex: Fix (possible) missed wakeup Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 40/77] locking/rwsem: " Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 41/77] libceph: avoid KEEPALIVE_PENDING races in ceph_con_keepalive() Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 42/77] dm: fix clone_bio() to trigger blk_recount_segments() Sasha Levin
2019-02-15 3:49 ` Mike Snitzer
2019-02-27 17:38 ` Sasha Levin
2019-02-27 18:48 ` Mike Snitzer
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 43/77] drm/amd/powerplay: OD setting fix on Vega10 Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 44/77] tty: serial: qcom_geni_serial: Allow mctrl when flow control is disabled Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 45/77] serial: fsl_lpuart: fix maximum acceptable baud rate with over-sampling Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 46/77] drm/sun4i: hdmi: Fix usage of TMDS clock Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 47/77] staging: android: ion: Support cpu access during dma_buf_detach Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 48/77] direct-io: allow direct writes to empty inodes Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 49/77] block: cover another queue enter recursion via BIO_QUEUE_ENTERED Sasha Levin
2019-02-15 2:24 ` Tetsuo Handa
2019-02-15 2:28 ` Ming Lei
2019-02-27 17:39 ` Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 50/77] writeback: synchronize sync(2) against cgroup writeback membership switches Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 51/77] scsi: lpfc: nvme: avoid hang / use-after-free when destroying localport Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 52/77] scsi: lpfc: nvmet: avoid hang / use-after-free when destroying targetport Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 53/77] scsi: csiostor: fix NULL pointer dereference in csio_vport_set_state() Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 54/77] net: altera_tse: fix connect_local_phy error path Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 55/77] hv_netvsc: Fix ethtool change hash key error Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 56/77] hv_netvsc: Refactor assignments of struct netvsc_device_info Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 57/77] hv_netvsc: Fix hash key value reset after other ops Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 58/77] sfc: suppress duplicate nvmem partition types in efx_ef10_mtd_probe Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 59/77] ax25: fix possible use-after-free Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 60/77] nvme-rdma: fix timeout handler Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 61/77] nvme-multipath: drop optimization for static ANA group IDs Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 62/77] cifs: fix memory leak of an allocated cifs_ntsd structure Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 63/77] drm/msm: Fix A6XX support for opp-level Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 64/77] drm/msm: avoid unused function warning Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 65/77] CIFS: Do not assume one credit for async responses Sasha Levin
2019-02-15 20:10 ` Pavel Shilovskiy
2019-02-27 17:54 ` Sasha Levin
2019-02-27 19:39 ` Pavel Shilovsky
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 66/77] CIFS: Fix mounts if the client is low on credits Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 67/77] net: usb: asix: ax88772_bind return error when hw_reset fail Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 68/77] net: dev_is_mac_header_xmit() true for ARPHRD_RAWIP Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 69/77] ibmveth: Do not process frames after calling napi_reschedule Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 70/77] mac80211: don't initiate TDLS connection if station is not associated to AP Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 71/77] mac80211: Add attribute aligned(2) to struct 'action' Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 72/77] cfg80211: extend range deviation for DMG Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 73/77] svm: Fix AVIC incomplete IPI emulation Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 74/77] KVM: nSVM: clear events pending from svm_complete_interrupts() when exiting to L1 Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 75/77] kvm: selftests: Fix region overlap check in kvm_util Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 76/77] KVM: selftests: check returned evmcs version range Sasha Levin
2019-02-15 2:08 ` [PATCH AUTOSEL 4.20 77/77] Revert "block: cover another queue enter recursion via BIO_QUEUE_ENTERED" Sasha Levin
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