For multiprocessor targets, do the thread_exit routine such that we don't need to rely on the compiler's good graces to have stack switching be reliable. Only needs a few asm instructions.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@26906 a1c6a512-1295-4272-9138-f99709370657

2 files changed, 29 insertions, 21 deletions

diff --git a/firmware/target/arm/thread-pp.c b/firmware/target/arm/thread-pp.c
index 335f1f3e0a..0c077779e5 100644
--- a/firmware/target/arm/thread-pp.c
+++ b/firmware/target/arm/thread-pp.c
@@ -199,7 +199,9 @@ static void INIT_ATTR core_thread_init(unsigned int core)
 }
 
 /*---------------------------------------------------------------------------
- * Switches to a stack that always resides in the Rockbox core.
+ * Switches to a stack that always resides in the Rockbox core then calls
+ * the final exit routine to actually finish removing the thread from the
+ * scheduler.
  *
  * Needed when a thread suicides on a core other than the main CPU since the
  * stack used when idling is the stack of the last thread to run. This stack
@@ -207,13 +209,24 @@ static void INIT_ATTR core_thread_init(unsigned int core)
  * to use a stack from an unloaded module until another thread runs on it.
  *---------------------------------------------------------------------------
  */
-static inline void switch_to_idle_stack(const unsigned int core)
+static inline void __attribute__((noreturn,always_inline))
+    thread_final_exit(struct thread_entry *current)
 {
     asm volatile (
-        "str  sp, [%0] \n" /* save original stack pointer on idle stack */
-        "mov  sp, %0   \n" /* switch stacks */
-        : : "r"(&idle_stacks[core][IDLE_STACK_WORDS-1]));
-    (void)core;
+        "cmp    %1, #0               \n" /* CPU? */
+        "ldrne  r0, =cpucache_flush  \n" /* No? write back data */
+        "movne  lr, pc               \n"
+        "bxne   r0                   \n"
+        "mov    r0, %0               \n" /* copy thread parameter */
+        "mov    sp, %2               \n" /* switch to idle stack  */
+        "bl     thread_final_exit_do \n" /* finish removal        */
+        : : "r"(current),
+            "r"(current->core),
+            "r"(&idle_stacks[current->core][IDLE_STACK_WORDS])
+        : "r0", "r1", "r2", "r3", "ip", "lr"); /* Because of flush call,
+                                                  force inputs out
+                                                  of scratch regs */
+    while (1);
 }
 
 /*---------------------------------------------------------------------------
diff --git a/firmware/thread.c b/firmware/thread.c
index de9d05da88..c00fc36e3f 100644
--- a/firmware/thread.c
+++ b/firmware/thread.c
@@ -157,8 +157,8 @@ static inline void load_context(const void* addr)
         __attribute__((always_inline));
 
 #if NUM_CORES > 1
-static void thread_final_exit(struct thread_entry *current)
-    __attribute__((noinline, noreturn));
+static void thread_final_exit_do(struct thread_entry *current)
+    __attribute__((noinline, noreturn, used));
 #else
 static inline void thread_final_exit(struct thread_entry *current)
     __attribute__((always_inline, noreturn));
@@ -1675,22 +1675,16 @@ void thread_wait(unsigned int thread_id)
 /* This is done to foil optimizations that may require the current stack,
  * such as optimizing subexpressions that put variables on the stack that
  * get used after switching stacks. */
-static void thread_final_exit(struct thread_entry *current)
-{
 #if NUM_CORES > 1
-    cpucache_flush();
-
-    /* Switch to the idle stack if not on the main core (where "main"
-     * runs) - we can hope gcc doesn't need the old stack beyond this
-     * point. */
-    if (current->core != CPU)
-    {
-        switch_to_idle_stack(current->core);
-    }
-
+/* Called by ASM stub */
+static void thread_final_exit_do(struct thread_entry *current)
+#else
+/* No special procedure is required before calling */
+static inline void thread_final_exit(struct thread_entry *current)
+#endif
+{
     /* At this point, this thread isn't using resources allocated for
      * execution except the slot itself. */
-#endif /* NUM_CORES */
 
     /* Signal this thread */
     thread_queue_wake(&current->queue);
@@ -1746,6 +1740,7 @@ void thread_exit(void)
     new_thread_id(current->id, current);
     current->name = NULL;
 
+    /* Do final cleanup and remove the thread */
     thread_final_exit(current);
 }