Pull documentation updates from Jonathan Corbet:
"Things have calmed down a bit on the docs front, with no earthshaking
changes this time around:
- Ongoing work on the Japanese and Portuguese translations
- Better integration of the MAINTAINERS file into the rendered
documents, including a search interface
- A seemingly infinite supply of fixes for typos, minor grammatical
issues, and related problems that LLMs find with abandon"
* tag 'docs-7.2' of git://git.kernel.org/pub/scm/linux/kernel/git/docs/linux: (93 commits)
docs: pt_BR: Translate 3.Early-stage.rst into Portuguese
docs: pt_BR: update "Purpose of Defconfigs" section in maintainer-soc.rst
Documentation: bug-hunting.rst: fix grammar
docs/ja_JP: translate submitting-patches.rst (interleaved-replies)
docs: Fix minor grammatical error
docs/{it_it,sp_SP,zh_CN,zh_TW}: update references to removed CONFIG_DEBUG_SLAB
Documentation: process: fix brackets
Documentation: arch: fix brackets
docs/dyndbg: explain flags parse 1st
docs/dyndbg: update examples \012 to \n
docs: kernel-parameters: Fix stale sticore file paths
docs: real-time: Fix duplicated sched(7) text
docs: kgdb: Fix stale source file paths
docs: sonypi: Fix stale header file path
docs: kernel-parameters: Remove sa1100ir IrDA parameter
iommu: Documentation: rearrange, update kernel-parameters
docs: md: fix grammar in speed_limit description
docs: changes.rst: restore pahole 1.26 minimum (regressed by sort)
Documentation: Fix syntax of kmalloc_objs example in coding style doc
docs: pt_BR: update maintainer-handbooks
...
The root document usually has a special :ref:`genindex` link to the
generated index. This is also the case for Documentation/index.rst. The
other index.rst files deeper in the directory hierarchy usually don't.
For SPHINXDIRS builds, the root document isn't Documentation/index.rst,
but some other index.rst in the hierarchy. Currently they have a
".. only::" block to add the index link when doing SPHINXDIRS html
builds.
This is obviously very tedious and repetitive. The link is also added to
all index.rst files in the hierarchy for SPHINXDIRS builds, not just the
root document.
Put the boilerplate in a sphinx-includes/subproject-index.rst file, and
include it at the end of the root document for subproject builds in an
ad-hoc source-read extension defined in conf.py.
For now, keep having the boilerplate in translations, because this
approach currently doesn't cover translated index link headers.
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Tested-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Reviewed-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
[jc: did s/doctree/kern_doc_dir/ ]
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20260123143149.2024303-1-jani.nikula@intel.com>
The comments and pseudo code in Documentation/locking/seqlock.rst are wrong:
int seq = 0;
do {
read_seqbegin_or_lock(&foo_seqlock, &seq);
/* ... [[read-side critical section]] ... */
} while (need_seqretry(&foo_seqlock, seq));
read_seqbegin_or_lock() always returns with an even "seq" and need_seqretry()
doesn't change this counter. This means that seq is always even and thus the
locking pass is simply impossible.
IOW, "_or_lock" has no effect and this code doesn't differ from
do {
seq = read_seqbegin(&foo_seqlock);
/* ... [[read-side critical section]] ... */
} while (read_seqretry(&foo_seqlock, seq));
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
While fuzzing an arm64 kernel, Alexander Potapenko reported:
| BUG: KCSAN: data-race in ktime_get_mono_fast_ns / timekeeping_update
|
| write to 0xffffffc082e74248 of 56 bytes by interrupt on cpu 0:
| update_fast_timekeeper kernel/time/timekeeping.c:430 [inline]
| timekeeping_update+0x1d8/0x2d8 kernel/time/timekeeping.c:768
| timekeeping_advance+0x9e8/0xb78 kernel/time/timekeeping.c:2344
| update_wall_time+0x18/0x38 kernel/time/timekeeping.c:2360
| [...]
|
| read to 0xffffffc082e74258 of 8 bytes by task 5260 on cpu 1:
| __ktime_get_fast_ns kernel/time/timekeeping.c:372 [inline]
| ktime_get_mono_fast_ns+0x88/0x174 kernel/time/timekeeping.c:489
| init_srcu_struct_fields+0x40c/0x530 kernel/rcu/srcutree.c:263
| init_srcu_struct+0x14/0x20 kernel/rcu/srcutree.c:311
| [...]
|
| value changed: 0x000002f875d33266 -> 0x000002f877416866
|
| Reported by Kernel Concurrency Sanitizer on:
| CPU: 1 UID: 0 PID: 5260 Comm: syz.2.7483 Not tainted 6.12.0-rc3-dirty #78
This is a false positive data race between a seqcount latch writer and a reader
accessing stale data. Since its introduction, KCSAN has never understood the
seqcount_latch interface (due to being unannotated).
Unlike the regular seqlock interface, the seqcount_latch interface for latch
writers never has had a well-defined critical section, making it difficult to
teach tooling where the critical section starts and ends.
Introduce an instrumentable (non-raw) seqcount_latch interface, with
which we can clearly denote writer critical sections. This both helps
readability and tooling like KCSAN to understand when the writer is done
updating all latch copies.
Fixes: 88ecd153be ("seqlock, kcsan: Add annotations for KCSAN")
Reported-by: Alexander Potapenko <glider@google.com>
Co-developed-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Signed-off-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20241104161910.780003-4-elver@google.com
I have seen several cases of attempts to use mutex_unlock() to release an
object such that the object can then be freed by another task.
This is not safe because mutex_unlock(), in the
MUTEX_FLAG_WAITERS && !MUTEX_FLAG_HANDOFF case, accesses the mutex
structure after having marked it as unlocked; so mutex_unlock() requires
its caller to ensure that the mutex stays alive until mutex_unlock()
returns.
If MUTEX_FLAG_WAITERS is set and there are real waiters, those waiters
have to keep the mutex alive, but we could have a spurious
MUTEX_FLAG_WAITERS left if an interruptible/killable waiter bailed
between the points where __mutex_unlock_slowpath() did the cmpxchg
reading the flags and where it acquired the wait_lock.
( With spinlocks, that kind of code pattern is allowed and, from what I
remember, used in several places in the kernel. )
Document this, such a semantic difference between mutexes and spinlocks
is fairly unintuitive.
[ mingo: Made the changelog a bit more assertive, refined the comments. ]
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20231130204817.2031407-1-jannh@google.com
Unless it was duplicate on purpose, to emphasize that a raw_spinlock_t
is always a spinning lock regardless of PREEMPT_RT or kernel config,
it's a bit odd that this text is duplicate. So, this patch just clean
it up, keeping the consistency with the other sections of the text.
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 919e9e6395 ("Documentation: Add lock ordering and nesting documentation")
Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Link: https://lore.kernel.org/r/20220321144133.49804-1-gpiccoli@igalia.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
The initial implementation of migrate_disable() for mainline was a
wrapper around preempt_disable(). RT kernels substituted this with
a real migrate disable implementation.
Later on mainline gained true migrate disable support, but the
documentation was not updated.
Update the documentation, remove the claims about migrate_disable()
mapping to preempt_disable() on non-PREEMPT_RT kernels.
Fixes: 74d862b682 ("sched: Make migrate_disable/enable() independent of RT")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211127163200.10466-2-bigeasy@linutronix.de
