From acc786cb5805d057932ada3e7c571bb8e901cd67 Mon Sep 17 00:00:00 2001 From: Alex Auvolat Date: Sat, 6 Dec 2014 23:15:06 +0100 Subject: Begin review of taking model : making things thread safe. --- kernel/lib/mutex.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) create mode 100644 kernel/lib/mutex.c (limited to 'kernel/lib/mutex.c') diff --git a/kernel/lib/mutex.c b/kernel/lib/mutex.c new file mode 100644 index 0000000..cda8049 --- /dev/null +++ b/kernel/lib/mutex.c @@ -0,0 +1,27 @@ +#include + +/* Internal use only. This function is atomic, meaning it cannot be interrupted by a system task switch. */ +static uint32_t atomic_exchange(uint32_t* ptr, uint32_t newval) { + uint32_t r; + asm volatile("xchg (%%ecx), %%eax" : "=a"(r) : "c"(ptr), "a"(newval)); + return r; +} + +void mutex_lock(uint32_t* mutex) { + while (atomic_exchange(mutex, MUTEX_LOCKED) == MUTEX_LOCKED) { + yield(); + } +} + +int mutex_try_lock(uint32_t* mutex) { + if (atomic_exchange(mutex, MUTEX_LOCKED) == MUTEX_LOCKED) { + return 0; + } + return 1; +} + +void mutex_unlock(uint32_t* mutex) { + *mutex = MUTEX_UNLOCKED; +} + +/* vim: set ts=4 sw=4 tw=0 noet :*/ -- cgit v1.2.3