memory barrier functions available for drivers.

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@25183 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/os/drivers/KernelExport.h

@@ -154,6 +154,8 @@ extern status_t		unregister_kernel_daemon(daemon_hook hook, void *arg);
 
 extern void			call_all_cpus(void (*func)(void *, int), void *cookie);
 extern void			call_all_cpus_sync(void (*func)(void *, int), void *cookie);
+extern void			memory_read_barrier(void);
+extern void			memory_write_barrier(void);
 
 /* safe methods to access user memory without having to lock it */
 extern status_t		user_memcpy(void *to, const void *from, size_t size);

headers/private/kernel/arch/cpu.h

@@ -41,6 +41,10 @@ status_t arch_cpu_user_memset(void *s, char c, size_t count,
 void arch_cpu_idle(void);
 void arch_cpu_sync_icache(void *address, size_t length);
 
+void arch_cpu_memory_read_barrier(void);
+void arch_cpu_memory_write_barrier(void);
+
+
 #ifdef __cplusplus
 }
 #endif 

src/system/kernel/arch/m68k/arch_cpu.cpp

@@ -110,6 +110,22 @@ arch_cpu_sync_icache(void *address, size_t len)
 }
 
 
+void
+arch_cpu_memory_read_barrier(void)
+{
+	asm volatile ("nop;" : : : "memory");
+#warning M68k: check arch_cpu_memory_read_barrier
+}
+
+
+void
+arch_cpu_memory_write_barrier(void)
+{
+	asm volatile ("nop;" : : : "memory");
+#warning M68k: check arch_cpu_memory_write_barrier
+}
+
+
 void 
 arch_cpu_invalidate_TLB_range(addr_t start, addr_t end)
 {

src/system/kernel/arch/ppc/arch_cpu.cpp

@@ -82,6 +82,23 @@ arch_cpu_sync_icache(void *address, size_t len)
 }
 
 
+void
+arch_cpu_memory_read_barrier(void)
+{
+#warning PPC: is it model-dependant ?
+	asm volatile ("lwsync");
+}
+
+
+void
+arch_cpu_memory_write_barrier(void)
+{
+#warning PPC: is it model-dependant ?
+	asm volatile ("isync");
+	asm volatile ("eioio");
+}
+
+
 void 
 arch_cpu_invalidate_TLB_range(addr_t start, addr_t end)
 {

src/system/kernel/arch/x86/arch_cpu.c

@@ -713,3 +713,19 @@ arch_cpu_sync_icache(void *address, size_t length)
 	// instruction cache is always consistent on x86
 }
 
+
+void
+arch_cpu_memory_read_barrier(void)
+{
+	asm volatile ("lock;" : : : "memory");
+	asm volatile ("addl $0,0(%%esp);" : : : "memory");
+}
+
+
+void
+arch_cpu_memory_write_barrier(void)
+{
+	asm volatile ("lock;" : : : "memory");
+	asm volatile ("addl $0,0(%%esp);" : : : "memory");
+}
+

src/system/kernel/smp.c

@@ -681,3 +681,17 @@ call_all_cpus_sync(void (*func)(void *, int), void *cookie)
 	restore_interrupts(state);
 }
 
+
+void
+memory_read_barrier(void)
+{
+	arch_cpu_memory_read_barrier();
+}
+
+
+void
+memory_write_barrier(void)
+{
+	arch_cpu_memory_write_barrier();
+}
+