X-Git-Url: https://codewiz.org/gitweb?a=blobdiff_plain;ds=inline;f=bertos%2Fkern%2Fproc.h;h=4efdf9df8e073e4d0a1ff41783dcdf9b32d7c2b0;hb=1200cce6f786accd1e56bfe1982b3c58d297aee7;hp=8a18bf7447c8fcc623cddefccfb89734ea82c704;hpb=cf6017f59fb2ff71423c716ad9d9f60a1b65c7d0;p=bertos.git

diff --git a/bertos/kern/proc.h b/bertos/kern/proc.h
index 8a18bf74..4efdf9df 100644
--- a/bertos/kern/proc.h
+++ b/bertos/kern/proc.h
@@ -46,6 +46,7 @@
 #endif
 
 #include <cpu/types.h> // cpustack_t
+#include <cpu/frame.h> // CPU_SAVED_REGS_CNT
 
 /*
  * Forward declaration. The definition of struct Process is private to the
@@ -65,7 +66,6 @@ struct Process *proc_new_with_name(const char* name, void (*entry)(void), iptr_t
 
 void proc_exit(void);
 void proc_yield(void);
-#define proc_switch proc_yield /* OBSOLETE */
 
 int proc_testSetup(void);
 int proc_testRun(void);
@@ -78,7 +78,11 @@ const char *proc_name(struct Process *proc);
 const char *proc_currentName(void);
 
 #if CONFIG_KERN_PRI
-void proc_setPri(struct Process *proc, int pri);
+	void proc_setPri(struct Process *proc, int pri);
+#else
+	INLINE void proc_setPri(UNUSED_ARG(struct Process *,proc), UNUSED_ARG(int, pri))
+	{
+	}
 #endif
 
 /**
@@ -91,6 +95,9 @@ void proc_setPri(struct Process *proc, int pri);
  * \note Calling functions that could sleep while task switching is disabled
  * is dangerous and unsupported.
  *
+ * \note calling proc_forbid() from within an interrupt is illegal and
+ * meaningless.
+ *
  * \note proc_permit() expands inline to 1-2 asm instructions, so it's a
  * very efficient locking primitive in simple but performance-critical
  * situations.  In all other cases, semaphores offer a more flexible and
@@ -101,12 +108,34 @@ void proc_setPri(struct Process *proc, int pri);
 INLINE void proc_forbid(void)
 {
 	#if CONFIG_KERN_PREEMPT
-		// No need to protect against interrupts here.
-		extern int preempt_forbid_cnt;
-		++preempt_forbid_cnt;
+		extern cpuatomic_t _preempt_forbid_cnt;
+		/*
+		 * We don't need to protect the counter against other processes.
+		 * The reason why is a bit subtle.
+		 *
+		 * If a process gets here, preempt_forbid_cnt can be either 0,
+		 * or != 0.  In the latter case, preemption is already disabled
+		 * and no concurrency issues can occur.
+		 *
+		 * In the former case, we could be preempted just after reading the
+		 * value 0 from memory, and a concurrent process might, in fact,
+		 * bump the value of preempt_forbid_cnt under our nose!
+		 *
+		 * BUT: if this ever happens, then we won't get another chance to
+		 * run until the other process calls proc_permit() to re-enable
+		 * preemption.  At this point, the value of preempt_forbid_cnt
+		 * must be back to 0, and thus what we had originally read from
+		 * memory happens to be valid.
+		 *
+		 * No matter how hard you think about it, and how complicated you
+		 * make your scenario, the above holds true as long as
+		 * "preempt_forbid_cnt != 0" means that no task switching is
+		 * possible.
+		 */
+		++_preempt_forbid_cnt;
 
 		/*
-		 * Make sure preempt_forbid_cnt is flushed to memory so the
+		 * Make sure _preempt_forbid_cnt is flushed to memory so the
 		 * preemption softirq will see the correct value from now on.
 		 */
 		MEMORY_BARRIER;
@@ -127,14 +156,13 @@ INLINE void proc_permit(void)
 		 * flushed to memory before task switching is re-enabled.
 		 */
 		MEMORY_BARRIER;
-
+		extern cpuatomic_t _preempt_forbid_cnt;
 		/* No need to protect against interrupts here. */
-		extern int preempt_forbid_cnt;
-		--preempt_forbid_cnt;
-		ASSERT(preempt_forbid_cnt >= 0);
+		ASSERT(_preempt_forbid_cnt != 0);
+		--_preempt_forbid_cnt;
 
 		/*
-		 * This ensures preempt_forbid_cnt is flushed to memory immediately
+		 * This ensures _preempt_forbid_cnt is flushed to memory immediately
 		 * so the preemption interrupt sees the correct value.
 		 */
 		MEMORY_BARRIER;
@@ -142,6 +170,20 @@ INLINE void proc_permit(void)
 	#endif
 }
 
+/**
+ * \return true if preemptive task switching is allowed.
+ * \note This accessor is needed because _preempt_forbid_cnt
+ *       must be absoultely private.
+ */
+INLINE bool proc_allowed(void)
+{
+	#if CONFIG_KERN_PREEMPT
+		extern cpuatomic_t _preempt_forbid_cnt;
+		return (_preempt_forbid_cnt == 0);
+	#else
+		return true;
+	#endif
+}
 
 /**
  * Execute a block of \a CODE atomically with respect to task scheduling.
@@ -184,8 +226,6 @@ INLINE void proc_permit(void)
 	#endif
 #endif
 
-#define CONFIG_PROC_DEFSTACKSIZE CONFIG_KERN_MINSTACKSIZE // OBSOLETE
-
 /* Memory fill codes to help debugging */
 #if CONFIG_KERN_MONITOR
 	#include <cpu/types.h>