FreeCalypso > hg > fc-tourmaline
view src/gpf/osl/os_tim_fl.c @ 220:0ed36de51973
ABB semaphore protection overhaul
The ABB semaphone protection logic that came with TCS211 from TI
was broken in several ways:
* Some semaphore-protected functions were called from Application_Initialize()
context. NU_Obtain_Semaphore() called with NU_SUSPEND fails with
NU_INVALID_SUSPEND in this context, but the return value wasn't checked,
and NU_Release_Semaphore() would be called unconditionally at the end.
The latter call would increment the semaphore count past 1, making the
semaphore no longer binary and thus no longer effective for resource
protection. The fix is to check the return value from NU_Obtain_Semaphore()
and skip the NU_Release_Semaphore() call if the semaphore wasn't properly
obtained.
* Some SPI hardware manipulation was being done before entering the semaphore-
protected critical section. The fix is to reorder the code: first obtain
the semaphore, then do everything else.
* In the corner case of L1/DSP recovery, l1_abb_power_on() would call some
non-semaphore-protected ABB & SPI init functions. The fix is to skip those
calls in the case of recovery.
* A few additional corner cases existed, all of which are fixed by making
ABB semaphore protection 100% consistent for all ABB functions and code paths.
There is still one remaining problem of priority inversion: suppose a low-
priority task calls an ABB function, and some medium-priority task just happens
to preempt right in the middle of that semaphore-protected ABB operation. Then
the high-priority SPI task is locked out for a non-deterministic time until
that medium-priority task finishes its work and goes back to sleep. This
priority inversion problem remains outstanding for now.
author | Mychaela Falconia <falcon@freecalypso.org> |
---|---|
date | Mon, 26 Apr 2021 20:55:25 +0000 |
parents | 4e78acac3d88 |
children |
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/* * This C module is a reconstruction based on the disassembly of * os_tim.obj in frame_na7_db_fl.lib from the Leonardo package, * subsequently reworked by Space Falcon. */ /* set of included headers from COFF symtab: */ #include <stdio.h> #include "nucleus.h" #include "typedefs.h" #include "os.h" #include "gdi.h" #include "os_types.h" #include "os_glob.h" extern UNSIGNED TMD_Timer; extern INT TMD_Timer_State; extern T_OS_TIMER_ENTRY TimerTable[]; extern T_OS_TIMER_TABLE_ENTRY *p_list[]; extern void os_Timeout(UNSIGNED t_handle); extern void timer_error(int err); unsigned os_time_to_tick_multiplier = TIME_TO_TICK_TDMA_FRAME_MULTIPLIER; unsigned os_tick_to_time_multiplier = TICK_TO_TIME_TDMA_FRAME_MULTIPLIER; unsigned volatile t_start_ticks; T_OS_TIMER_TABLE_ENTRY *t_running; int used_timers; int next_t_handle; int volatile t_list_access; int max_used_timers; NU_SEMAPHORE TimSemCB; NU_TIMER os_timer_cb; #ifdef __GNUC__ #define BARRIER asm volatile ("": : :"memory") #else #define BARRIER /* prayer */ #endif GLOBAL LONG os_set_tick(int os_system_tick) { switch (os_system_tick) { case SYSTEM_TICK_TDMA_FRAME: os_time_to_tick_multiplier = TIME_TO_TICK_TDMA_FRAME_MULTIPLIER; os_tick_to_time_multiplier = TICK_TO_TIME_TDMA_FRAME_MULTIPLIER; return(OS_OK); case SYSTEM_TICK_10_MS: os_time_to_tick_multiplier = TIME_TO_TICK_10MS_MULTIPLIER; os_tick_to_time_multiplier = TICK_TO_TIME_10MS_MULTIPLIER; return(OS_OK); default: return(OS_ERROR); } } GLOBAL LONG os_TimerInformation(USHORT Index, char *Buffer) { static int t_info_read; if (t_info_read) { t_info_read = 0; return(OS_ERROR); } sprintf(Buffer, "Maximum %d of %d available timers running", max_used_timers, MaxSimultaneousTimer); t_info_read = 1; return(OS_OK); } GLOBAL LONG os_TimInit(void) { int i; if (NU_Create_Semaphore(&TimSemCB, "TIMSEM", 1, NU_PRIORITY) != NU_SUCCESS) return(OS_ERROR); if (NU_Create_Timer(&os_timer_cb, "OS_TIMER", os_Timeout, 0, 1, 0, NU_DISABLE_TIMER) != NU_SUCCESS) return(OS_ERROR); used_timers = 0; max_used_timers = 0; next_t_handle = 1; t_list_access = 0; t_start_ticks = 0; p_list[0] = 0; for (i = 1; i < MaxSimultaneousTimer; i++) { TimerTable[i].entry.status = TMR_FREE; TimerTable[i].entry.next = 0; TimerTable[i].entry.prev = 0; TimerTable[i].next_t_handle = i + 1; p_list[i] = 0; } TimerTable[MaxSimultaneousTimer].entry.status = TMR_FREE; TimerTable[MaxSimultaneousTimer].next_t_handle = 0; t_running = 0; return(OS_OK); } GLOBAL LONG os_RecoverTick(OS_TICK ticks) { UNSIGNED current_system_clock; current_system_clock = NU_Retrieve_Clock(); NU_Set_Clock(current_system_clock + ticks); if (TMD_Timer_State == TM_ACTIVE) { if (TMD_Timer <= ticks) { TMD_Timer_State = TM_EXPIRED; TMD_Timer = 0; } else TMD_Timer -= ticks; } return(OS_OK); } GLOBAL LONG os_QueryTimer(OS_HANDLE TaskHandle, OS_HANDLE TimerHandle, OS_TIME *RemainingTime) { T_OS_TIMER_TABLE_ENTRY *timer, *t_iter; OS_TICK c_ticks, r_ticks, e_ticks; STATUS sts; if (TimerHandle > MaxSimultaneousTimer) return(OS_ERROR); sts = NU_Obtain_Semaphore(&TimSemCB, NU_SUSPEND); timer = &TimerTable[TimerHandle].entry; if (timer->status == TMR_FREE) { if (sts == NU_SUCCESS) NU_Release_Semaphore(&TimSemCB); return(OS_ERROR); } t_list_access = 1; BARRIER; if (!t_running) { r_ticks = 0; goto out; } c_ticks = NU_Retrieve_Clock(); e_ticks = c_ticks - t_start_ticks; t_iter = t_running; if (t_iter->r_ticks >= e_ticks) r_ticks = t_iter->r_ticks - e_ticks; else r_ticks = 0; while (t_iter != timer) { t_iter = t_iter->next; if (t_iter == t_running) { r_ticks = 0; goto out; } r_ticks += t_iter->r_ticks; } out: BARRIER; t_list_access = 0; if (sts == NU_SUCCESS) NU_Release_Semaphore(&TimSemCB); *RemainingTime = SYSTEM_TICKS_TO_TIME(r_ticks); return(OS_OK); } GLOBAL LONG os_InactivityTicks(int *next_event, OS_TICK *next_event_ticks) { *next_event = 1; switch (TMD_Timer_State) { case TM_ACTIVE: *next_event_ticks = TMD_Timer; return(OS_OK); case TM_NOT_ACTIVE: *next_event_ticks = 0; *next_event = 0; return(OS_OK); default: *next_event_ticks = 0; return(OS_OK); } }