From 43db8c57ebe496bea03d66e2ddd0aa6bc298738c Mon Sep 17 00:00:00 2001 From: Christian Cunningham Date: Sun, 19 Dec 2021 14:50:45 -0800 Subject: Added atomic swap --- src/cpu/atomic/swap.a.h | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) create mode 100644 src/cpu/atomic/swap.a.h (limited to 'src/cpu') diff --git a/src/cpu/atomic/swap.a.h b/src/cpu/atomic/swap.a.h new file mode 100644 index 0000000..63dd50b --- /dev/null +++ b/src/cpu/atomic/swap.a.h @@ -0,0 +1,32 @@ +#ifndef CPU_ATOMIC_SWAP_A_H +#define CPU_ATOMIC_SWAP_A_H + +/// https://stackoverflow.com/questions/16329123/use-of-strexeq-instead-of-strex-for-spinlock-implementation-in-arm + +static inline void atm_lock(unsigned long pid, unsigned long* addr) { + unsigned long tmp, current_lock_value; + asm volatile( +"1: ldrex %0, [%3]\n" +" cmp %0, #0\n" +" wfene\n" +" strexeq %1, %2, [%3]\n" +" teq %1, #0\n" +" bne 1b\n" +" dmb" + : "=&r" (current_lock_value), "=&r" (tmp) + : "r" (pid), "r" (addr) + : "cc"); +} + +static inline void atm_unlock(unsigned long* addr) { + unsigned long cleared = 0; + asm volatile( +" dmb\n" +" str %0, [%1]\n" +" dsb\n" +" sev" + :: "r" (cleared), "r" (addr) + : "cc"); +} + +#endif -- cgit v1.2.1