kernel/linux.git/include/linux/atomic/atomic-instrumented.h, branch v6.6.132

locking/atomic: scripts: fix ${atomic}_sub_and_test() kerneldoc

2024-06-27T11:49:11+00:00

commit f92a59f6d12e31ead999fee9585471b95a8ae8a3 upstream. For ${atomic}_sub_and_test() the @i parameter is the value to subtract, not add. Fix the typo in the kerneldoc template and generate the headers with this update. Fixes: ad8110706f38 ("locking/atomic: scripts: generate kerneldoc comments") Suggested-by: Mark Rutland Signed-off-by: Carlos Llamas Signed-off-by: Peter Zijlstra (Intel) Acked-by: Mark Rutland Reviewed-by: Kees Cook Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20240515133844.3502360-1-cmllamas@google.com [cmllamas: generate headers with gen-atomics.sh] Signed-off-by: Carlos Llamas Signed-off-by: Greg Kroah-Hartman

locking/atomic: scripts: fix ${atomic}_dec_if_positive() kerneldoc

2023-06-16T14:46:30+00:00

The ${atomic}_dec_if_positive() ops are unlike all the other conditional atomic ops. Rather than returning a boolean success value, these return the value that the atomic variable would be updated to, even when no update is performed. We missed this when adding kerneldoc comments, and the documentation for ${atomic}_dec_if_positive() erroneously states: | Return: @true if @v was updated, @false otherwise. Ideally we'd clean this up by aligning ${atomic}_dec_if_positive() with the usual atomic op conventions: with ${atomic}_fetch_dec_if_positive() for those who care about the value of the varaible, and ${atomic}_dec_if_positive() returning a boolean success value. In the mean time, align the documentation with the current reality. Fixes: ad8110706f381170 ("locking/atomic: scripts: generate kerneldoc comments") Signed-off-by: Mark Rutland Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Paul E. McKenney Link: https://lore.kernel.org/r/20230615132734.1119765-1-mark.rutland@arm.com

locking/atomic: scripts: generate kerneldoc comments

2023-06-05T07:57:23+00:00

Currently the atomics are documented in Documentation/atomic_t.txt, and have no kerneldoc comments. There are a sufficient number of gotchas (e.g. semantics, noinstr-safety) that it would be nice to have comments to call these out, and it would be nice to have kerneldoc comments such that these can be collated. While it's possible to derive the semantics from the code, this can be painful given the amount of indirection we currently have (e.g. fallback paths), and it's easy to be mislead by naming, e.g. * The unconditional void-returning ops *only* have relaxed variants without a _relaxed suffix, and can easily be mistaken for being fully ordered. It would be nice to give these a _relaxed() suffix, but this would result in significant churn throughout the kernel. * Our naming of conditional and unconditional+test ops is rather inconsistent, and it can be difficult to derive the name of an operation, or to identify where an op is conditional or unconditional+test. Some ops are clearly conditional: - dec_if_positive - add_unless - dec_unless_positive - inc_unless_negative Some ops are clearly unconditional+test: - sub_and_test - dec_and_test - inc_and_test However, what exactly those test is not obvious. A _test_zero suffix might be clearer. Others could be read ambiguously: - inc_not_zero // conditional - add_negative // unconditional+test It would probably be worth renaming these, e.g. to inc_unless_zero and add_test_negative. As a step towards making this more consistent and easier to understand, this patch adds kerneldoc comments for all generated *atomic*_*() functions. These are generated from templates, with some common text shared, making it easy to extend these in future if necessary. I've tried to make these as consistent and clear as possible, and I've deliberately ensured: * All ops have their ordering explicitly mentioned in the short and long description. * All test ops have "test" in their short description. * All ops are described as an expression using their usual C operator. For example: andnot: "Atomically updates @v to (@v & ~@i)" inc: "Atomically updates @v to (@v + 1)" Which may be clearer to non-naative English speakers, and allows all the operations to be described in the same style. * All conditional ops have their condition described as an expression using the usual C operators. For example: add_unless: "If (@v != @u), atomically updates @v to (@v + @i)" cmpxchg: "If (@v == @old), atomically updates @v to @new" Which may be clearer to non-naative English speakers, and allows all the operations to be described in the same style. * All bitwise ops (and,andnot,or,xor) explicitly mention that they are bitwise in their short description, so that they are not mistaken for performing their logical equivalents. * The noinstr safety of each op is explicitly described, with a description of whether or not to use the raw_ form of the op. There should be no functional change as a result of this patch. Reported-by: Paul E. McKenney Signed-off-by: Mark Rutland Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Kees Cook Link: https://lore.kernel.org/r/20230605070124.3741859-26-mark.rutland@arm.com

locking/atomic: scripts: simplify raw_atomic*() definitions

2023-06-05T07:57:22+00:00

Currently each ordering variant has several potential definitions, with a mixture of preprocessor and C definitions, including several copies of its C prototype, e.g. | #if defined(arch_atomic_fetch_andnot_acquire) | #define raw_atomic_fetch_andnot_acquire arch_atomic_fetch_andnot_acquire | #elif defined(arch_atomic_fetch_andnot_relaxed) | static __always_inline int | raw_atomic_fetch_andnot_acquire(int i, atomic_t *v) | { | int ret = arch_atomic_fetch_andnot_relaxed(i, v); | __atomic_acquire_fence(); | return ret; | } | #elif defined(arch_atomic_fetch_andnot) | #define raw_atomic_fetch_andnot_acquire arch_atomic_fetch_andnot | #else | static __always_inline int | raw_atomic_fetch_andnot_acquire(int i, atomic_t *v) | { | return raw_atomic_fetch_and_acquire(~i, v); | } | #endif Make this a bit simpler by defining the C prototype once, and writing the various potential definitions as plain C code guarded by ifdeffery. For example, the above becomes: | static __always_inline int | raw_atomic_fetch_andnot_acquire(int i, atomic_t *v) | { | #if defined(arch_atomic_fetch_andnot_acquire) | return arch_atomic_fetch_andnot_acquire(i, v); | #elif defined(arch_atomic_fetch_andnot_relaxed) | int ret = arch_atomic_fetch_andnot_relaxed(i, v); | __atomic_acquire_fence(); | return ret; | #elif defined(arch_atomic_fetch_andnot) | return arch_atomic_fetch_andnot(i, v); | #else | return raw_atomic_fetch_and_acquire(~i, v); | #endif | } Which is far easier to read. As we now always have a single copy of the C prototype wrapping all the potential definitions, we now have an obvious single location for kerneldoc comments. At the same time, the fallbacks for raw_atomic*_xhcg() are made to use 'new' rather than 'i' as the name of the new value. This is what the existing fallback template used, and is more consistent with the raw_atomic{_try,}cmpxchg() fallbacks. There should be no functional change as a result of this patch. Signed-off-by: Mark Rutland Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Kees Cook Link: https://lore.kernel.org/r/20230605070124.3741859-24-mark.rutland@arm.com

locking/atomic: scripts: add trivial raw_atomic*_()

2023-06-05T07:57:19+00:00

Currently a number of arch_atomic*_() functions are optional, and where an arch does not provide a given arch_atomic*_() we will define an implementation of arch_atomic*_() in atomic-arch-fallback.h. Filling in the missing ops requires special care as we want to select the optimal definition of each op (e.g. preferentially defining ops in terms of their relaxed form rather than their fully-ordered form). The ifdeffery necessary for this requires us to group ordering variants together, which can be a bit painful to read, and is painful for kerneldoc generation. It would be easier to handle this if we generated ops into a separate namespace, as this would remove the need to take special care with the ifdeffery, and allow each ordering variant to be generated separately. This patch adds a new set of raw_atomic_() definitions, which are currently trivial wrappers of their arch_atomic_() equivalent. This will allow us to move treewide users of arch_atomic_() over to raw atomic op before we rework the fallback generation to generate raw_atomic_ directly. There should be no functional change as a result of this patch. Signed-off-by: Mark Rutland Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Kees Cook Link: https://lore.kernel.org/r/20230605070124.3741859-18-mark.rutland@arm.com

arch: Remove cmpxchg_double

2023-06-05T07:36:39+00:00

No moar users, remove the monster. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Arnd Bergmann Reviewed-by: Mark Rutland Acked-by: Heiko Carstens Tested-by: Mark Rutland Link: https://lore.kernel.org/r/20230531132323.991907085@infradead.org

instrumentation: Wire up cmpxchg128()

2023-06-05T07:36:36+00:00

Wire up the cmpxchg128 family in the atomic wrapper scripts. These provide the generic cmpxchg128 family of functions from the arch_ prefixed version, adding explicit instrumentation where needed. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Arnd Bergmann Reviewed-by: Mark Rutland Acked-by: Mark Rutland Tested-by: Mark Rutland Link: https://lore.kernel.org/r/20230531132323.519237070@infradead.org

locking/atomic: Correct (cmp)xchg() instrumentation

2023-04-29T07:09:31+00:00

All xchg() and cmpxchg() ops are atomic RMWs, but currently we instrument these with instrument_atomic_write() rather than instrument_atomic_read_write(), missing the read aspect. Similarly, all try_cmpxchg() ops are non-atomic RMWs on *oldp, but we instrument these accesses with instrument_atomic_write() rather than instrument_read_write(), missing the read aspect and erroneously marking these as atomic. Fix the instrumentation for both points. Signed-off-by: Mark Rutland Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Link: https://lkml.kernel.org/r/20230413160644.490976-1-mark.rutland@arm.com Cc: Linus Torvalds

locking/atomic: Add generic try_cmpxchg{,64}_local() support

2023-04-29T07:09:02+00:00

Add generic support for try_cmpxchg{,64}_local() and their falbacks. These provides the generic try_cmpxchg_local family of functions from the arch_ prefixed version, also adding explicit instrumentation. Signed-off-by: Uros Bizjak Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Acked-by: Mark Rutland Link: https://lore.kernel.org/r/20230405141710.3551-2-ubizjak@gmail.com Cc: Linus Torvalds

atomics: Provide atomic_add_negative() variants

2023-03-28T08:39:29+00:00

atomic_add_negative() does not provide the relaxed/acquire/release variants. Provide them in preparation for a new scalable reference count algorithm. Signed-off-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Acked-by: Mark Rutland Link: https://lore.kernel.org/r/20230323102800.101763813@linutronix.de