From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Valentin Schneider <valentin.schneider@arm.com>,
Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.4 31/32] kthread: Extract KTHREAD_IS_PER_CPU
Date: Fri, 5 Feb 2021 15:07:46 +0100 [thread overview]
Message-ID: <20210205140653.666133800@linuxfoundation.org> (raw)
In-Reply-To: <20210205140652.348864025@linuxfoundation.org>
From: Peter Zijlstra <peterz@infradead.org>
[ Upstream commit ac687e6e8c26181a33270efd1a2e2241377924b0 ]
There is a need to distinguish geniune per-cpu kthreads from kthreads
that happen to have a single CPU affinity.
Geniune per-cpu kthreads are kthreads that are CPU affine for
correctness, these will obviously have PF_KTHREAD set, but must also
have PF_NO_SETAFFINITY set, lest userspace modify their affinity and
ruins things.
However, these two things are not sufficient, PF_NO_SETAFFINITY is
also set on other tasks that have their affinities controlled through
other means, like for instance workqueues.
Therefore another bit is needed; it turns out kthread_create_per_cpu()
already has such a bit: KTHREAD_IS_PER_CPU, which is used to make
kthread_park()/kthread_unpark() work correctly.
Expose this flag and remove the implicit setting of it from
kthread_create_on_cpu(); the io_uring usage of it seems dubious at
best.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Tested-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210121103506.557620262@infradead.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/linux/kthread.h | 3 +++
kernel/kthread.c | 27 ++++++++++++++++++++++++++-
kernel/smpboot.c | 1 +
3 files changed, 30 insertions(+), 1 deletion(-)
diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index 0f9da966934e2..c7108ce5a051c 100644
--- a/include/linux/kthread.h
+++ b/include/linux/kthread.h
@@ -31,6 +31,9 @@ struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
unsigned int cpu,
const char *namefmt);
+void kthread_set_per_cpu(struct task_struct *k, int cpu);
+bool kthread_is_per_cpu(struct task_struct *k);
+
/**
* kthread_run - create and wake a thread.
* @threadfn: the function to run until signal_pending(current).
diff --git a/kernel/kthread.c b/kernel/kthread.c
index e51f0006057df..1d4c98a19043f 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -469,11 +469,36 @@ struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
return p;
kthread_bind(p, cpu);
/* CPU hotplug need to bind once again when unparking the thread. */
- set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags);
to_kthread(p)->cpu = cpu;
return p;
}
+void kthread_set_per_cpu(struct task_struct *k, int cpu)
+{
+ struct kthread *kthread = to_kthread(k);
+ if (!kthread)
+ return;
+
+ WARN_ON_ONCE(!(k->flags & PF_NO_SETAFFINITY));
+
+ if (cpu < 0) {
+ clear_bit(KTHREAD_IS_PER_CPU, &kthread->flags);
+ return;
+ }
+
+ kthread->cpu = cpu;
+ set_bit(KTHREAD_IS_PER_CPU, &kthread->flags);
+}
+
+bool kthread_is_per_cpu(struct task_struct *k)
+{
+ struct kthread *kthread = to_kthread(k);
+ if (!kthread)
+ return false;
+
+ return test_bit(KTHREAD_IS_PER_CPU, &kthread->flags);
+}
+
/**
* kthread_unpark - unpark a thread created by kthread_create().
* @k: thread created by kthread_create().
diff --git a/kernel/smpboot.c b/kernel/smpboot.c
index 2efe1e206167c..f25208e8df836 100644
--- a/kernel/smpboot.c
+++ b/kernel/smpboot.c
@@ -188,6 +188,7 @@ __smpboot_create_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
kfree(td);
return PTR_ERR(tsk);
}
+ kthread_set_per_cpu(tsk, cpu);
/*
* Park the thread so that it could start right on the CPU
* when it is available.
--
2.27.0
next prev parent reply other threads:[~2021-02-05 17:53 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-05 14:07 [PATCH 5.4 00/32] 5.4.96-rc1 review Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 01/32] net: dsa: bcm_sf2: put device node before return Greg Kroah-Hartman
2021-02-07 9:25 ` Pavel Machek
2021-02-05 14:07 ` [PATCH 5.4 02/32] net: switchdev: dont set port_obj_info->handled true when -EOPNOTSUPP Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 03/32] ibmvnic: Ensure that CRQ entry read are correctly ordered Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 04/32] Revert "Revert "block: end bio with BLK_STS_AGAIN in case of non-mq devs and REQ_NOWAIT"" Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 05/32] ACPI: thermal: Do not call acpi_thermal_check() directly Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 06/32] arm64: Fix kernel address detection of __is_lm_address() Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 07/32] arm64: Do not pass tagged addresses to __is_lm_address() Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 08/32] tcp: make TCP_USER_TIMEOUT accurate for zero window probes Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 09/32] btrfs: backref, only collect file extent items matching backref offset Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 10/32] btrfs: backref, dont add refs from shared block when resolving normal backref Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 11/32] btrfs: backref, only search backref entries from leaves of the same root Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 12/32] btrfs: backref, use correct count to resolve normal data refs Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 13/32] net_sched: gen_estimator: support large ewma log Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 14/32] phy: cpcap-usb: Fix warning for missing regulator_disable Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 15/32] platform/x86: touchscreen_dmi: Add swap-x-y quirk for Goodix touchscreen on Estar Beauty HD tablet Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 16/32] platform/x86: intel-vbtn: Support for tablet mode on Dell Inspiron 7352 Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 17/32] x86: __always_inline __{rd,wr}msr() Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 18/32] scsi: scsi_transport_srp: Dont block target in failfast state Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 19/32] scsi: libfc: Avoid invoking response handler twice if ep is already completed Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 20/32] scsi: fnic: Fix memleak in vnic_dev_init_devcmd2 Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 21/32] ASoC: SOF: Intel: hda: Resume codec to do jack detection Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 22/32] mac80211: fix fast-rx encryption check Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 23/32] scsi: ibmvfc: Set default timeout to avoid crash during migration Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 24/32] ALSA: hda: Add Cometlake-R PCI ID Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 25/32] udf: fix the problem that the disc content is not displayed Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 26/32] nvme: check the PRINFO bit before deciding the host buffer length Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 27/32] selftests/powerpc: Only test lwm/stmw on big endian Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 28/32] drm/amd/display: Update dram_clock_change_latency for DCN2.1 Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 29/32] drm/amd/display: Change function decide_dp_link_settings to avoid infinite looping Greg Kroah-Hartman
2021-02-05 14:07 ` [PATCH 5.4 30/32] objtool: Dont fail on missing symbol table Greg Kroah-Hartman
2021-02-05 14:07 ` Greg Kroah-Hartman [this message]
2021-02-05 14:07 ` [PATCH 5.4 32/32] workqueue: Restrict affinity change to rescuer Greg Kroah-Hartman
2021-02-05 20:58 ` [PATCH 5.4 00/32] 5.4.96-rc1 review Igor
2021-02-05 21:16 ` Florian Fainelli
2021-02-07 14:36 ` Greg Kroah-Hartman
2021-02-06 14:27 ` Naresh Kamboju
2021-02-06 16:02 ` Guenter Roeck
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