linux/scripts/atomic/fallbacks/try_cmpxchg

cat <<EOF
static inline bool
${atomic}_try_cmpxchg${order}(${atomic}_t *v, ${int} *old, ${int} new)
{
	${int} r, o = *old;
	r = ${atomic}_cmpxchg${order}(v, o, new);
	if (unlikely(r != o))
		*old = r;
	return likely(r == o);
}
EOF
locking/atomics: Add common header generation files To minimize repetition, to allow for future rework, and to ensure regularity of the various atomic APIs, we'd like to automatically generate (the bulk of) a number of headers related to atomics. This patch adds the infrastructure to do so, leaving actual conversion of headers to subsequent patches. This infrastructure consists of: * atomics.tbl - a table describing the functions in the atomics API, with names, prototypes, and metadata describing the variants that exist (e.g fetch/return, acquire/release/relaxed). Note that the return type is dependent on the particular variant. * atomic-tbl.sh - a library of routines useful for dealing with atomics.tbl (e.g. querying which variants exist, or generating argument/parameter lists for a given function variant). * gen-atomic-fallback.sh - a script which generates a header of fallbacks, covering cases where architecture omit certain functions (e.g. omitting relaxed variants). * gen-atomic-long.sh - a script which generates wrappers providing the atomic_long API atomic of the relevant atomic or atomic64 API, ensuring the APIs are consistent. * gen-atomic-instrumented.sh - a script which generates atomic* wrappers atop of arch_atomic* functions, with automatically generated KASAN instrumentation. * fallbacks/* - a set of fallback implementations for atomics, which should be used when no implementation of a given atomic is provided. These are used by gen-atomic-fallback.sh to generate fallbacks, and these are also used by other scripts to determine the set of optional atomics (as required to generate preprocessor guards correctly). Fallbacks may use the following variables: ${atomic} atomic prefix: atomic/atomic64/atomic_long, which can be used to derive the atomic type, and to prefix functions ${int} integer type: int/s64/long ${pfx} variant prefix, e.g. fetch_ ${name} base function name, e.g. add ${sfx} variant suffix, e.g. _return ${order} order suffix, e.g. _relaxed ${atomicname} full name, e.g. atomic64_fetch_add_relaxed ${ret} return type of the function, e.g. void ${retstmt} a return statement (with a trailing space), unless the variant returns void ${params} parameter list for the function declaration, e.g. "int i, atomic_t *v" ${args} argument list for invoking the function, e.g. "i, v" ... for clarity, ${ret}, ${retstmt}, ${params}, and ${args} are open-coded for fallbacks where these do not vary, or are critical to understanding the logic of the fallback. The MAINTAINERS entry for the atomic infrastructure is updated to cover the new scripts. There should be no functional change as a result of this patch. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: linux-arm-kernel@lists.infradead.org Cc: catalin.marinas@arm.com Cc: Will Deacon <will.deacon@arm.com> Cc: linuxdrivers@attotech.com Cc: dvyukov@google.com Cc: Boqun Feng <boqun.feng@gmail.com> Cc: arnd@arndb.de Cc: aryabinin@virtuozzo.com Cc: glider@google.com Link: http://lkml.kernel.org/r/20180904104830.2975-2-mark.rutland@arm.com Signed-off-by: Ingo Molnar <mingo@kernel.org> 2018-09-04 10:48:25 +00:00			`cat <<EOF`
			`static inline bool`
			`${atomic}_try_cmpxchg${order}(${atomic}_t v, ${int} old, ${int} new)`
			`{`
			`${int} r, o = *old;`
			`r = ${atomic}_cmpxchg${order}(v, o, new);`
			`if (unlikely(r != o))`
			`*old = r;`
			`return likely(r == o);`
			`}`
			`EOF`