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Filename Latest commit message Latest commit date
Hector Martin d0c4307aea locking/atomic: Make test_and_*_bit() ordered on failure
commit 415d832497098030241605c52ea83d4e2cfa7879 upstream.

These operations are documented as always ordered in
include/asm-generic/bitops/instrumented-atomic.h, and producer-consumer
type use cases where one side needs to ensure a flag is left pending
after some shared data was updated rely on this ordering, even in the
failure case.

This is the case with the workqueue code, which currently suffers from a
reproducible ordering violation on Apple M1 platforms (which are
notoriously out-of-order) that ends up causing the TTY layer to fail to
deliver data to userspace properly under the right conditions.  This
change fixes that bug.

Change the documentation to restrict the "no order on failure" story to
the _lock() variant (for which it makes sense), and remove the
early-exit from the generic implementation, which is what causes the
missing barrier semantics in that case.  Without this, the remaining
atomic op is fully ordered (including on ARM64 LSE, as of recent
versions of the architecture spec).

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: stable@vger.kernel.org
Fixes: e986a0d6cb ("locking/atomics, asm-generic/bitops/atomic.h: Rewrite using atomic_*() APIs")
Fixes: 61e02392d3 ("locking/atomic/bitops: Document and clarify ordering semantics for failed test_and_{}_bit()")
Signed-off-by: Hector Martin <marcan@marcan.st>
Acked-by: Will Deacon <will@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-08-25 11:18:31 +02:00
arch powerpc/pci: Fix get_phb_number() locking 2022-08-25 11:18:29 +02:00
block blk-mq: don't create hctx debugfs dir until q->debugfs_dir is created 2022-08-25 11:17:36 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:11:22 +02:00
crypto crypto: drbg - make reseeding from get_random_bytes() synchronous 2022-06-22 14:11:18 +02:00
Documentation locking/atomic: Make test_and_*_bit() ordered on failure 2022-08-25 11:18:31 +02:00
drivers igb: Add lock to avoid data race 2022-08-25 11:18:30 +02:00
fs NFSv4/pnfs: Fix a use-after-free bug in open 2022-08-25 11:18:22 +02:00
include locking/atomic: Make test_and_*_bit() ordered on failure 2022-08-25 11:18:31 +02:00
init random: handle latent entropy and command line from random_init() 2022-06-22 14:11:17 +02:00
ipc
kernel tracing: Have filter accept "common_cpu" to be consistent 2022-08-25 11:18:19 +02:00
lib locking/refcount: Consolidate implementations of refcount_t 2022-07-29 17:14:17 +02:00
LICENSES
mm mm/mmap.c: fix missing call to vm_unacct_memory in mmap_region 2022-08-25 11:17:58 +02:00
net netfilter: nf_tables: really skip inactive sets when allocating name 2022-08-25 11:18:29 +02:00
samples
scripts gcc-plugins: Undefine LATENT_ENTROPY_PLUGIN when plugin disabled for a file 2022-08-25 11:18:31 +02:00
security apparmor: Fix memleak in aa_simple_write_to_buffer() 2022-08-25 11:18:21 +02:00
sound ALSA: info: Fix llseek return value when using callback 2022-08-25 11:18:18 +02:00
tools tools build: Switch to new openssl API for test-libcrypto 2022-08-25 11:18:25 +02:00
usr
virt KVM: Add infrastructure and macro to mark VM as bugged 2022-08-25 11:18:16 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS MAINTAINERS: co-maintain random.c 2022-06-22 14:11:05 +02:00
Makefile Makefile: link with -z noexecstack --no-warn-rwx-segments 2022-08-25 11:17:17 +02:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
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    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.