From f5baaf48e3e82b1caf9f5cd1207d4d6feba3a2e5 Mon Sep 17 00:00:00 2001 From: Thomas Bertschinger Date: Mon, 15 Jan 2024 23:41:02 -0700 Subject: move Rust sources to top level, C sources into c_src This moves the Rust sources out of rust_src/ and into the top level. Running the bcachefs executable out of the development tree is now: $ ./target/release/bcachefs command or $ cargo run --profile release -- command instead of "./bcachefs command". Building and installing is still: $ make && make install Signed-off-by: Thomas Bertschinger Signed-off-by: Kent Overstreet --- c_src/linux/preempt.c | 37 +++++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) create mode 100644 c_src/linux/preempt.c (limited to 'c_src/linux/preempt.c') diff --git a/c_src/linux/preempt.c b/c_src/linux/preempt.c new file mode 100644 index 00000000..72eceed3 --- /dev/null +++ b/c_src/linux/preempt.c @@ -0,0 +1,37 @@ +#include + +#include "linux/preempt.h" + +/* + * In userspace, pthreads are preemptible and can migrate CPUs at any time. + * + * In the kernel, preempt_disable() logic essentially guarantees that a marked + * critical section owns its CPU for the relevant block. This is necessary for + * various code paths, critically including the percpu system as it allows for + * non-atomic reads and writes to CPU-local data structures. + * + * The high performance userspace equivalent would be to use thread local + * storage to replace percpu data, but that would be complicated. It should be + * correct to instead guarantee mutual exclusion for the critical sections. + */ + +static pthread_mutex_t preempt_lock; + +__attribute__((constructor)) +static void preempt_init(void) { + pthread_mutexattr_t attr; + pthread_mutexattr_init(&attr); + pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE); + pthread_mutex_init(&preempt_lock, &attr); + pthread_mutexattr_destroy(&attr); +} + +void preempt_disable(void) +{ + pthread_mutex_lock(&preempt_lock); +} + +void preempt_enable(void) +{ + pthread_mutex_unlock(&preempt_lock); +} -- cgit v1.2.3