Linus Torvalds 1d6d399223 Kthreads affinity follow either of 4 existing different patterns: ... 1) Per-CPU kthreads must stay affine to a single CPU and never execute relevant code on any other CPU. This is currently handled by smpboot code which takes care of CPU-hotplug operations. Affinity here is a correctness constraint. 2) Some kthreads _have_ to be affine to a specific set of CPUs and can't run anywhere else. The affinity is set through kthread_bind_mask() and the subsystem takes care by itself to handle CPU-hotplug operations. Affinity here is assumed to be a correctness constraint. 3) Per-node kthreads _prefer_ to be affine to a specific NUMA node. This is not a correctness constraint but merely a preference in terms of memory locality. kswapd and kcompactd both fall into this category. The affinity is set manually like for any other task and CPU-hotplug is supposed to be handled by the relevant subsystem so that the task is properly reaffined whenever a given CPU from the node comes up. Also care should be taken so that the node affinity doesn't cross isolated (nohz_full) cpumask boundaries. 4) Similar to the previous point except kthreads have a _preferred_ affinity different than a node. Both RCU boost kthreads and RCU exp kworkers fall into this category as they refer to "RCU nodes" from a distinctly distributed tree. Currently the preferred affinity patterns (3 and 4) have at least 4 identified users, with more or less success when it comes to handle CPU-hotplug operations and CPU isolation. Each of which do it in its own ad-hoc way. This is an infrastructure proposal to handle this with the following API changes: _ kthread_create_on_node() automatically affines the created kthread to its target node unless it has been set as per-cpu or bound with kthread_bind[_mask]() before the first wake-up. - kthread_affine_preferred() is a new function that can be called right after kthread_create_on_node() to specify a preferred affinity different than the specified node. When the preferred affinity can't be applied because the possible targets are offline or isolated (nohz_full), the kthread is affine to the housekeeping CPUs (which means to all online CPUs most of the time or only the non-nohz_full CPUs when nohz_full= is set). kswapd, kcompactd, RCU boost kthreads and RCU exp kworkers have been converted, along with a few old drivers. Summary of the changes: * Consolidate a bunch of ad-hoc implementations of kthread_run_on_cpu() * Introduce task_cpu_fallback_mask() that defines the default last resort affinity of a task to become nohz_full aware * Add some correctness check to ensure kthread_bind() is always called before the first kthread wake up. * Default affine kthread to its preferred node. * Convert kswapd / kcompactd and remove their halfway working ad-hoc affinity implementation * Implement kthreads preferred affinity * Unify kthread worker and kthread API's style * Convert RCU kthreads to the new API and remove the ad-hoc affinity implementation. -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEd76+gtGM8MbftQlOhSRUR1COjHcFAmeNf8gACgkQhSRUR1CO jHedQQ/+IxTjjqQiItzrq41TES2S0desHDq8lNJFb7rsR/DtKFyLx3s67cOYV+cM Yx54QHg2m/Fz4nXMQ7Po5ygOtJGCKBc5C5QQy7y0lVKeTQK+daDfEtBSa3oG7j3C u+E3tTY6qxkbCzymUyaKkHN4/ay2vLvjFS50luV7KMyI3x47Aji+t7VdCX4LCPP2 eAwOALWD0+7qLJ/VF6gsmQLKA4Qx7PQAzBa3KSBmUN9UcN8Gk1bQHCTIQKDHP9LQ v8BXrNZtYX1o2+snNYpX2z6/ECjxkdwriOgqqZY5306hd9RAQ1u46Dx3byrIqjGn ULG/XQ2istPyhTqb/h+RbrobdOcwEUIeqk8hRRbBXE8bPpqUz9EMuaCMxWDbQjgH NTuKG4ifKJ/IqstkkuDkdOiByE/ysMmwqrTXgSnu2ITNL9yY3BEgFbvA95hgo42s f7QCxEfZb1MHcNEMENSMwM3xw5lLMGMpxVZcMQ3gLwyotMBRrhFZm1qZJG7TITYW IDIeCbH4JOMdQwLs3CcWTXio0N5/85NhRNFV+IDn96OrgxObgnMtV8QwNgjXBAJ5 wGeJWt8s34W1Zo3qS9gEuVzEhW4XaxISQQMkHe8faKkK6iHmIB/VjSQikDwwUNQ/ AspYj82RyWBCDZsqhiYh71kpxjvS6Xp0bj39Ce1sNsOnuksxKkQ= =g8In -----END PGP SIGNATURE----- Merge tag 'kthread-for-6.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks Pull kthread updates from Frederic Weisbecker: "Kthreads affinity follow either of 4 existing different patterns: 1) Per-CPU kthreads must stay affine to a single CPU and never execute relevant code on any other CPU. This is currently handled by smpboot code which takes care of CPU-hotplug operations. Affinity here is a correctness constraint. 2) Some kthreads _have_ to be affine to a specific set of CPUs and can't run anywhere else. The affinity is set through kthread_bind_mask() and the subsystem takes care by itself to handle CPU-hotplug operations. Affinity here is assumed to be a correctness constraint. 3) Per-node kthreads _prefer_ to be affine to a specific NUMA node. This is not a correctness constraint but merely a preference in terms of memory locality. kswapd and kcompactd both fall into this category. The affinity is set manually like for any other task and CPU-hotplug is supposed to be handled by the relevant subsystem so that the task is properly reaffined whenever a given CPU from the node comes up. Also care should be taken so that the node affinity doesn't cross isolated (nohz_full) cpumask boundaries. 4) Similar to the previous point except kthreads have a _preferred_ affinity different than a node. Both RCU boost kthreads and RCU exp kworkers fall into this category as they refer to "RCU nodes" from a distinctly distributed tree. Currently the preferred affinity patterns (3 and 4) have at least 4 identified users, with more or less success when it comes to handle CPU-hotplug operations and CPU isolation. Each of which do it in its own ad-hoc way. This is an infrastructure proposal to handle this with the following API changes: - kthread_create_on_node() automatically affines the created kthread to its target node unless it has been set as per-cpu or bound with kthread_bind[_mask]() before the first wake-up. - kthread_affine_preferred() is a new function that can be called right after kthread_create_on_node() to specify a preferred affinity different than the specified node. When the preferred affinity can't be applied because the possible targets are offline or isolated (nohz_full), the kthread is affine to the housekeeping CPUs (which means to all online CPUs most of the time or only the non-nohz_full CPUs when nohz_full= is set). kswapd, kcompactd, RCU boost kthreads and RCU exp kworkers have been converted, along with a few old drivers. Summary of the changes: - Consolidate a bunch of ad-hoc implementations of kthread_run_on_cpu() - Introduce task_cpu_fallback_mask() that defines the default last resort affinity of a task to become nohz_full aware - Add some correctness check to ensure kthread_bind() is always called before the first kthread wake up. - Default affine kthread to its preferred node. - Convert kswapd / kcompactd and remove their halfway working ad-hoc affinity implementation - Implement kthreads preferred affinity - Unify kthread worker and kthread API's style - Convert RCU kthreads to the new API and remove the ad-hoc affinity implementation" * tag 'kthread-for-6.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks: kthread: modify kernel-doc function name to match code rcu: Use kthread preferred affinity for RCU exp kworkers treewide: Introduce kthread_run_worker[_on_cpu]() kthread: Unify kthread_create_on_cpu() and kthread_create_worker_on_cpu() automatic format rcu: Use kthread preferred affinity for RCU boost kthread: Implement preferred affinity mm: Create/affine kswapd to its preferred node mm: Create/affine kcompactd to its preferred node kthread: Default affine kthread to its preferred NUMA node kthread: Make sure kthread hasn't started while binding it sched,arm64: Handle CPU isolation on last resort fallback rq selection arm64: Exclude nohz_full CPUs from 32bits el0 support lib: test_objpool: Use kthread_run_on_cpu() kallsyms: Use kthread_run_on_cpu() soc/qman: test: Use kthread_run_on_cpu() arm/bL_switcher: Use kthread_run_on_cpu()		2025-01-21 17:10:05 -08:00
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acquirewdt.c
advantech_ec_wdt.c
advantechwdt.c
airoha_wdt.c
alim1535_wdt.c
alim7101_wdt.c
apple_wdt.c
arm_smc_wdt.c
armada_37xx_wdt.c
asm9260_wdt.c
aspeed_wdt.c
at91rm9200_wdt.c
at91sam9_wdt.c
at91sam9_wdt.h
ath79_wdt.c
bcm47xx_wdt.c
bcm2835_wdt.c
bcm7038_wdt.c
bcm_kona_wdt.c
bd9576_wdt.c
bd96801_wdt.c
booke_wdt.c
cadence_wdt.c
cgbc_wdt.c
cpwd.c
cros_ec_wdt.c
da9052_wdt.c
da9055_wdt.c
da9062_wdt.c
da9063_wdt.c
davinci_wdt.c
db8500_wdt.c
diag288_wdt.c
digicolor_wdt.c
dw_wdt.c
ebc-c384_wdt.c
ep93xx_wdt.c
eurotechwdt.c
exar_wdt.c
f71808e_wdt.c
ftwdt010_wdt.c
gef_wdt.c
geodewdt.c
gpio_wdt.c
gxp-wdt.c
hpwdt.c
i6300esb.c
ib700wdt.c
ibmasr.c
ie6xx_wdt.c
imgpdc_wdt.c
imx2_wdt.c
imx7ulp_wdt.c
imx_sc_wdt.c
indydog.c
intel-mid_wdt.c
it87_wdt.c
it8712f_wdt.c
iTCO_vendor.h
iTCO_vendor_support.c
iTCO_wdt.c
ixp4xx_wdt.c
jz4740_wdt.c
Kconfig
keembay_wdt.c
kempld_wdt.c
lantiq_wdt.c
lenovo_se10_wdt.c
loongson1_wdt.c
lpc18xx_wdt.c
m54xx_wdt.c
machzwd.c
Makefile
marvell_gti_wdt.c
max63xx_wdt.c
max77620_wdt.c
mei_wdt.c
mena21_wdt.c
menf21bmc_wdt.c
menz69_wdt.c
meson_gxbb_wdt.c
meson_wdt.c
mixcomwd.c
mlx_wdt.c
moxart_wdt.c
mpc8xxx_wdt.c
msc313e_wdt.c
mt7621_wdt.c
mtk_wdt.c
mtx-1_wdt.c
ni903x_wdt.c
nic7018_wdt.c
npcm_wdt.c
nv_tco.c
nv_tco.h
octeon-wdt-main.c
octeon-wdt-nmi.S
of_xilinx_wdt.c
omap_wdt.c
omap_wdt.h
orion_wdt.c
pc87413_wdt.c
pcwd.c
pcwd_pci.c
pcwd_usb.c
pic32-dmt.c
pic32-wdt.c
pika_wdt.c
pm8916_wdt.c
pnx4008_wdt.c
pretimeout_noop.c
pretimeout_panic.c
pseries-wdt.c
qcom-wdt.c
rave-sp-wdt.c
rc32434_wdt.c
rdc321x_wdt.c
realtek_otto_wdt.c
renesas_wdt.c
retu_wdt.c
riowd.c
rn5t618_wdt.c
rt2880_wdt.c
rtd119x_wdt.c
rti_wdt.c
rza_wdt.c
rzg2l_wdt.c
rzn1_wdt.c
rzv2h_wdt.c
s3c2410_wdt.c
sa1100_wdt.c
sama5d4_wdt.c
sb_wdog.c
sbc60xxwdt.c
sbc7240_wdt.c
sbc8360.c
sbc_epx_c3.c
sbc_fitpc2_wdt.c
sbsa_gwdt.c
sc520_wdt.c
sc1200wdt.c
sch311x_wdt.c
scx200_wdt.c
shwdt.c
simatic-ipc-wdt.c
sl28cpld_wdt.c
smsc37b787_wdt.c
softdog.c
sp805_wdt.c
sp5100_tco.c
sp5100_tco.h
sprd_wdt.c
st_lpc_wdt.c
starfive-wdt.c
stm32_iwdg.c
stmp3xxx_rtc_wdt.c
stpmic1_wdt.c
sun4v_wdt.c
sunplus_wdt.c
sunxi_wdt.c
tegra_wdt.c
tqmx86_wdt.c
ts72xx_wdt.c
ts4800_wdt.c
twl4030_wdt.c
txx9wdt.c
uniphier_wdt.c
via_wdt.c
visconti_wdt.c
w83627hf_wdt.c
w83877f_wdt.c
w83977f_wdt.c
wafer5823wdt.c
watchdog_core.c
watchdog_core.h
watchdog_dev.c
watchdog_hrtimer_pretimeout.c
watchdog_pretimeout.c
watchdog_pretimeout.h
wd501p.h
wdat_wdt.c
wdrtas.c
wdt.c
wdt285.c
wdt977.c
wdt_pci.c
wm831x_wdt.c
wm8350_wdt.c
xen_wdt.c
xilinx_wwdt.c
ziirave_wdt.c