From e586c178073b9a0fee90d5fc8e795d266ebd7b7d Mon Sep 17 00:00:00 2001 From: Vegard Storheil Eriksen Date: Tue, 7 Aug 2012 16:50:46 +0200 Subject: Initial import. Most sources are split off from suzumebachi project revision 2fc77d2 as is with some path changes. New build rules introduced. --- os/mutex.h | 42 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+) create mode 100644 os/mutex.h (limited to 'os/mutex.h') diff --git a/os/mutex.h b/os/mutex.h new file mode 100644 index 0000000..d12331d --- /dev/null +++ b/os/mutex.h @@ -0,0 +1,42 @@ +#ifndef MUTEX_H +#define MUTEX_H + +class Mutex { + private: + uint8_t locked; + public: + Mutex() : locked(0) {} + Mutex(uint8_t l) : locked(l) {} + + bool trylock() { + uint8_t val; + + // Check if mutex is locked. + asm volatile ("ldrexb %0, [%1]" : "=r" (val) : "r" (&locked)); + if(val) { + return false; + } + + // Try taking the lock. + asm volatile ("strexb %0, %1, [%2]" : "=r" (val) : "r" (1), "r" (&locked)); + if(val) { + return false; + } + + asm volatile("dmb"); + return true; + } + + void lock() { + while(!trylock()) { + Thread::yield(); + } + } + + void unlock() { + asm volatile("dmb"); + locked = 0; + } +}; + +#endif -- cgit v1.2.3