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author | Linus Torvalds <torvalds@linux-foundation.org> | 2021-09-01 18:49:47 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-09-01 18:49:47 -0700 |
commit | 4ac6d90867a4de2e12117e755dbd76e08d88697f (patch) | |
tree | cc6dae69b561f2cf797e7c823fbfa0e9d32236c5 /Documentation/core-api | |
parent | df43d903828c59afb9e93b59835127a02e1f8144 (diff) | |
parent | 37397b092e7f4b520a257aaafe83f868cd3d5e27 (diff) | |
download | linux-4ac6d90867a4de2e12117e755dbd76e08d88697f.tar.bz2 |
Merge tag 'docs-5.15' of git://git.lwn.net/linux
Pull documentation updates from Jonathan Corbet:
"Yet another set of documentation changes:
- A reworking of PDF generation to yield better results for documents
using CJK fonts in particular.
- A new set of translations into traditional Chinese, a dialect for
which I am assured there is a community of interested readers.
- A lot more regular Chinese translation work as well.
... plus the usual assortment of updates, fixes, typo tweaks, etc"
* tag 'docs-5.15' of git://git.lwn.net/linux: (55 commits)
docs: sphinx-requirements: Move sphinx_rtd_theme to top
docs: pdfdocs: Enable language-specific font choice of zh_TW translations
docs: pdfdocs: Teach xeCJK about character classes of quotation marks
docs: pdfdocs: Permit AutoFakeSlant for CJK fonts
docs: pdfdocs: One-half spacing for CJK translations
docs: pdfdocs: Add conf.py local to translations for ascii-art alignment
docs: pdfdocs: Preserve inter-phrase space in Korean translations
docs: pdfdocs: Choose Serif font as CJK mainfont if possible
docs: pdfdocs: Add CJK-language-specific font settings
docs: pdfdocs: Refactor config for CJK document
scripts/kernel-doc: Override -Werror from KCFLAGS with KDOC_WERROR
docs/zh_CN: Add zh_CN/accounting/psi.rst
doc: align Italian translation
Documentation/features/vm: riscv supports THP now
docs/zh_CN: add infiniband user_verbs translation
docs/zh_CN: add infiniband user_mad translation
docs/zh_CN: add infiniband tag_matching translation
docs/zh_CN: add infiniband sysfs translation
docs/zh_CN: add infiniband opa_vnic translation
docs/zh_CN: add infiniband ipoib translation
...
Diffstat (limited to 'Documentation/core-api')
-rw-r--r-- | Documentation/core-api/cpu_hotplug.rst | 38 | ||||
-rw-r--r-- | Documentation/core-api/printk-formats.rst | 1 |
2 files changed, 25 insertions, 14 deletions
diff --git a/Documentation/core-api/cpu_hotplug.rst b/Documentation/core-api/cpu_hotplug.rst index 1122cd3044c0..b66e3cae1472 100644 --- a/Documentation/core-api/cpu_hotplug.rst +++ b/Documentation/core-api/cpu_hotplug.rst @@ -91,9 +91,10 @@ Never use anything other than ``cpumask_t`` to represent bitmap of CPUs. Using CPU hotplug ================= + The kernel option *CONFIG_HOTPLUG_CPU* needs to be enabled. It is currently available on multiple architectures including ARM, MIPS, PowerPC and X86. The -configuration is done via the sysfs interface: :: +configuration is done via the sysfs interface:: $ ls -lh /sys/devices/system/cpu total 0 @@ -113,14 +114,14 @@ configuration is done via the sysfs interface: :: The files *offline*, *online*, *possible*, *present* represent the CPU masks. Each CPU folder contains an *online* file which controls the logical on (1) and -off (0) state. To logically shutdown CPU4: :: +off (0) state. To logically shutdown CPU4:: $ echo 0 > /sys/devices/system/cpu/cpu4/online smpboot: CPU 4 is now offline Once the CPU is shutdown, it will be removed from */proc/interrupts*, */proc/cpuinfo* and should also not be shown visible by the *top* command. To -bring CPU4 back online: :: +bring CPU4 back online:: $ echo 1 > /sys/devices/system/cpu/cpu4/online smpboot: Booting Node 0 Processor 4 APIC 0x1 @@ -142,6 +143,7 @@ The CPU hotplug coordination The offline case ---------------- + Once a CPU has been logically shutdown the teardown callbacks of registered hotplug states will be invoked, starting with ``CPUHP_ONLINE`` and terminating at state ``CPUHP_OFFLINE``. This includes: @@ -158,9 +160,10 @@ at state ``CPUHP_OFFLINE``. This includes: Using the hotplug API --------------------- + It is possible to receive notifications once a CPU is offline or onlined. This might be important to certain drivers which need to perform some kind of setup -or clean up functions based on the number of available CPUs: :: +or clean up functions based on the number of available CPUs:: #include <linux/cpuhotplug.h> @@ -186,9 +189,10 @@ During the removal of a hotplug state the teardown callback will be invoked. Multiple instances ~~~~~~~~~~~~~~~~~~ + If a driver has multiple instances and each instance needs to perform the callback independently then it is likely that a ''multi-state'' should be used. -First a multi-state state needs to be registered: :: +First a multi-state state needs to be registered:: ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, "X/Y:online, Y_online, Y_prepare_down); @@ -197,7 +201,7 @@ First a multi-state state needs to be registered: :: The ``cpuhp_setup_state_multi()`` behaves similar to ``cpuhp_setup_state()`` except it prepares the callbacks for a multi state and does not invoke the callbacks. This is a one time setup. -Once a new instance is allocated, you need to register this new instance: :: +Once a new instance is allocated, you need to register this new instance:: ret = cpuhp_state_add_instance(Y_hp_online, &d->node); @@ -206,7 +210,8 @@ This function will add this instance to your previously allocated (*Y_online*) on all online CPUs. The *node* element is a ``struct hlist_node`` member of your per-instance data structure. -On removal of the instance: :: +On removal of the instance:: + cpuhp_state_remove_instance(Y_hp_online, &d->node) should be invoked which will invoke the teardown callback on all online @@ -214,6 +219,7 @@ CPUs. Manual setup ~~~~~~~~~~~~ + Usually it is handy to invoke setup and teardown callbacks on registration or removal of a state because usually the operation needs to performed once a CPU goes online (offline) and during initial setup (shutdown) of the driver. However @@ -226,6 +232,7 @@ hotplug operations. The ordering of the events -------------------------- + The hotplug states are defined in ``include/linux/cpuhotplug.h``: * The states *CPUHP_OFFLINE* … *CPUHP_AP_OFFLINE* are invoked before the @@ -248,13 +255,14 @@ another hotplug event. Testing of hotplug states ========================= + One way to verify whether a custom state is working as expected or not is to shutdown a CPU and then put it online again. It is also possible to put the CPU to certain state (for instance *CPUHP_AP_ONLINE*) and then go back to *CPUHP_ONLINE*. This would simulate an error one state after *CPUHP_AP_ONLINE* which would lead to rollback to the online state. -All registered states are enumerated in ``/sys/devices/system/cpu/hotplug/states``: :: +All registered states are enumerated in ``/sys/devices/system/cpu/hotplug/states`` :: $ tail /sys/devices/system/cpu/hotplug/states 138: mm/vmscan:online @@ -268,7 +276,7 @@ All registered states are enumerated in ``/sys/devices/system/cpu/hotplug/states 168: sched:active 169: online -To rollback CPU4 to ``lib/percpu_cnt:online`` and back online just issue: :: +To rollback CPU4 to ``lib/percpu_cnt:online`` and back online just issue:: $ cat /sys/devices/system/cpu/cpu4/hotplug/state 169 @@ -276,14 +284,14 @@ To rollback CPU4 to ``lib/percpu_cnt:online`` and back online just issue: :: $ cat /sys/devices/system/cpu/cpu4/hotplug/state 140 -It is important to note that the teardown callbac of state 140 have been -invoked. And now get back online: :: +It is important to note that the teardown callback of state 140 have been +invoked. And now get back online:: $ echo 169 > /sys/devices/system/cpu/cpu4/hotplug/target $ cat /sys/devices/system/cpu/cpu4/hotplug/state 169 -With trace events enabled, the individual steps are visible, too: :: +With trace events enabled, the individual steps are visible, too:: # TASK-PID CPU# TIMESTAMP FUNCTION # | | | | | @@ -318,6 +326,7 @@ trace. Architecture's requirements =========================== + The following functions and configurations are required: ``CONFIG_HOTPLUG_CPU`` @@ -339,11 +348,12 @@ The following functions and configurations are required: User Space Notification ======================= -After CPU successfully onlined or offline udev events are sent. A udev rule like: :: + +After CPU successfully onlined or offline udev events are sent. A udev rule like:: SUBSYSTEM=="cpu", DRIVERS=="processor", DEVPATH=="/devices/system/cpu/*", RUN+="the_hotplug_receiver.sh" -will receive all events. A script like: :: +will receive all events. A script like:: #!/bin/sh diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst index d941717a191b..e08bbe9b0cbf 100644 --- a/Documentation/core-api/printk-formats.rst +++ b/Documentation/core-api/printk-formats.rst @@ -130,6 +130,7 @@ printed after the symbol name with an extra ``b`` appended to the end of the specifier. :: + %pS versatile_init+0x0/0x110 [module_name] %pSb versatile_init+0x0/0x110 [module_name ed5019fdf5e53be37cb1ba7899292d7e143b259e] %pSRb versatile_init+0x9/0x110 [module_name ed5019fdf5e53be37cb1ba7899292d7e143b259e] |