X-Git-Url: https://codewiz.org/gitweb?a=blobdiff_plain;f=bertos%2Fkern%2Fproc.h;h=e9a910d4d5fbc466ae7bc217f7e651103b4532a5;hb=e62ca0b357f09804d7d894949df44224c9d74bb7;hp=8a18bf7447c8fcc623cddefccfb89734ea82c704;hpb=cf6017f59fb2ff71423c716ad9d9f60a1b65c7d0;p=bertos.git diff --git a/bertos/kern/proc.h b/bertos/kern/proc.h index 8a18bf74..e9a910d4 100644 --- a/bertos/kern/proc.h +++ b/bertos/kern/proc.h @@ -45,7 +45,8 @@ #include // ASSERT() #endif -#include // cpustack_t +#include // cpu_stack_t +#include // CPU_SAVED_REGS_CNT /* * Forward declaration. The definition of struct Process is private to the @@ -55,7 +56,7 @@ struct Process; /* Task scheduling services */ void proc_init(void); -struct Process *proc_new_with_name(const char* name, void (*entry)(void), iptr_t data, size_t stacksize, cpustack_t *stack); +struct Process *proc_new_with_name(const char* name, void (*entry)(void), iptr_t data, size_t stacksize, cpu_stack_t *stack); #if !CONFIG_KERN_MONITOR #define proc_new(entry,data,size,stack) proc_new_with_name(NULL,(entry),(data),(size),(stack)) @@ -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 cpu_atomic_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 cpu_atomic_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 cpu_atomic_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. @@ -179,34 +221,32 @@ INLINE void proc_permit(void) * usage. */ #define CONFIG_KERN_MINSTACKSIZE \ - (CPU_SAVED_REGS_CNT * 2 * sizeof(cpustack_t) \ + (CPU_SAVED_REGS_CNT * 2 * sizeof(cpu_stack_t) \ + 32 * sizeof(int)) #endif #endif -#define CONFIG_PROC_DEFSTACKSIZE CONFIG_KERN_MINSTACKSIZE // OBSOLETE - /* Memory fill codes to help debugging */ #if CONFIG_KERN_MONITOR #include #if (SIZEOF_CPUSTACK_T == 1) - /* 8bit cpustack_t */ + /* 8bit cpu_stack_t */ #define CONFIG_KERN_STACKFILLCODE 0xA5 #define CONFIG_KERN_MEMFILLCODE 0xDB #elif (SIZEOF_CPUSTACK_T == 2) - /* 16bit cpustack_t */ + /* 16bit cpu_stack_t */ #define CONFIG_KERN_STACKFILLCODE 0xA5A5 #define CONFIG_KERN_MEMFILLCODE 0xDBDB #elif (SIZEOF_CPUSTACK_T == 4) - /* 32bit cpustack_t */ + /* 32bit cpu_stack_t */ #define CONFIG_KERN_STACKFILLCODE 0xA5A5A5A5UL #define CONFIG_KERN_MEMFILLCODE 0xDBDBDBDBUL #elif (SIZEOF_CPUSTACK_T == 8) - /* 64bit cpustack_t */ + /* 64bit cpu_stack_t */ #define CONFIG_KERN_STACKFILLCODE 0xA5A5A5A5A5A5A5A5ULL #define CONFIG_KERN_MEMFILLCODE 0xDBDBDBDBDBDBDBDBULL #else - #error No cpustack_t size supported! + #error No cpu_stack_t size supported! #endif #endif