Multi-threading: Difference between revisions

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 Though it is possible to run multi-threaded programs, running those on different cores is not possible "as-is". One core is always dedicated to the OS, hence you will never get 100% of both cores.
+Using CloseHandle() with a KThread handle will terminate the specified thread, only if the reference count reaches 0.
+Lower priority values give the thread higher priority. For userland apps, priorities between 0x18 and 0x3F are allowed. The priority of the app's main thread seems to be 0x30.
+The thread scheduler is cooperative, therefore if a thread takes up all the CPU time (for example if it enters an endless loop), all the other threads that run on the same CPU core won't get a chance to run. The main way of yielding another thread is using an address arbiter.
 == Usage ==
-=== CreateThread ===
+=== CreateThread (svc 0x08) ===
+'''Definition'''
+ Result CreateThread(Handle* thread, func entrypoint, u32 arg, u32 stacktop, s32 threadpriority, s32 processorid);
+'''Configuration'''
+ R0=s32 threadpriority
+ R1=func entrypoint
+ R2=u32 arg
+ R3=u32 stacktop
+ R4=s32 processorid
+ Result result=R0
+ Handle* thread=R1
+'''Details'''
+The processorid parameter specifies which processor the thread can run on. Non-negative values correspond to a specific CPU. (e.g. 0 for the Appcore and 1 for the Syscore on Old3DS) Special value -1 means all CPUs, and -2 means the default CPU for the process (Read from the [[NCCH/Extended Header|Exheader]], usually 0 for applications, 1 for system services). Games usually create threads using -2.
+With the Old3DS kernel, the s32 processorid must be <=2.
+With the New3DS kernel: processorid must be <= <total cores(MPCore "SCU Configuration Register" CPU number value + 1)>. When processorid==0x2 and the process is not an APPLICATION mem-region process, exheader kernel-flags bitmask 0x2000 must be set otherwise error 0xD9001BEA is returned. When processorid==0x3 and the process is not an APPLICATION mem-region process, error 0xD9001BEA is returned. These are the only restriction checks done by the kernel for processorid.
+The thread priority value must be in the following range: 0x0..0x3F.
+The stacktop must be aligned to 0x8-bytes, otherwise when not aligned to 0x8-bytes the ARM11 kernel clears the low 3-bits of the stacktop address.
+The input address used for Entrypoint_Param and StackTop are normally the same, however these can be arbitrary. For the main thread the Entrypoint_Param is value 0.
+=== ExitThread (svc 0x09)===
+'''Definition'''
+ void ExitThread(void);
+=== SleepThread (svc 0x0A)===
+'''Definition'''
+ void SleepThread(s64 nanoseconds);
+=== GetThreadPriority (svc 0x0B) ===
-=== ExitThread ===
+'''Definition'''
+ Result GetThreadPriority(s32* priority, Handle thread);
-=== SleepThread ===
+'''asm'''
+ .global svcGetThreadPriority
+ .type svcGetThreadPriority, %function
+ svcGetThreadPriority:
+ 	str r0, [sp, #-0x4]!
+ 	svc 0x0B
+ 	ldr r3, [sp], #4
+ 	str r1, [r3]
+ 	bx  lr
-=== GetThreadPriority ===
+=== SetThreadPriority (svc 0x0C) ===
-=== SetThreadPriority ===
+'''Definition'''
+ Result SetThreadPriority(Handle thread, s32 priority);
 === OpenThread ===
+'''Definition'''
+ Result OpenThread(Handle* thread, Handle process, u32 threadId);
 === GetProcessIdOfThread ===
+'''Definition'''
+ Result GetProcessIdOfThread(u32* processId, Handle thread);
 === GetThreadId ===
+'''Definition'''
+ Result GetThreadId(u32* threadId, Handle thread);
 === GetThreadInfo ===
+'''Definition'''
+ Result GetThreadInfo(s64* out, Handle thread, ThreadInfoType type);
+{| class="wikitable" border="1"
+!  ThreadInfoType value
+!  Description
+|-
+| ?
+| ?
+|}
 === GetThreadContext ===
+'''Definition'''
+ Result GetThreadContext(ThreadContext* context, Handle thread);
+'''Details'''
+Stubbed?
 == Core affinity ==
 === GetThreadAffinityMask ===
+'''Definition'''
+ Result GetThreadAffinityMask(u8* affinitymask, Handle thread, s32 processorcount);
 === SetThreadAffinityMask ===
+'''Definition'''
+ Result SetThreadAffinityMask(Handle thread, u8* affinitymask, s32 processorcount);
 === GetThreadIdealProcessor ===
+'''Definition'''
+ Result GetThreadIdealProcessor(s32* processorid, Handle thread);
 === SetThreadIdealProcessor ===
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 == Mutex (normal) ==
+For Kernel implementation details, see [[KMutex]]
 ===  CreateMutex ===