Revert "Fix race condition when tracing is enabled (#95)" (#149)
This reverts commit 61635d5b8b7ae1e783026f37eb66757509010130.
diff --git a/portable/GCC/ARM_CR5/port.c b/portable/GCC/ARM_CR5/port.c
index 970b304..8b9933f 100644
--- a/portable/GCC/ARM_CR5/port.c
+++ b/portable/GCC/ARM_CR5/port.c
@@ -146,20 +146,6 @@
#define portTASK_RETURN_ADDRESS prvTaskExitError
#endif
-
-/* Adding the necessary stuff in order to be able to determine from C code wheter or not the IRQs are enabled at the processor level (not interrupt controller level) */
-#define GET_CPSR() \
- ( { u32 rval = 0U; \
- __asm__ __volatile__ ( \
- "mrs %0, cpsr\n"\
- : "=r" ( rval ) \
- ); \
- rval; \
- } )
-
-#define CPSR_IRQ_ENABLE_MASK 0x80U
-
-#define IS_IRQ_DISABLED() ( { unsigned int val = 0; val = ( GET_CPSR() & CPSR_IRQ_ENABLE_MASK ) ? 1 : 0; val; } )
/*-----------------------------------------------------------*/
/*
@@ -481,12 +467,6 @@
uint32_t ulPortSetInterruptMask( void )
{
uint32_t ulReturn;
- uint32_t wasIRQDisabled;
-
- /* We keep track of if the IRQ are enabled in the CPU (as opposed to interrupts masked in the interrupt controller, like the intend of this function).
- * This is very important because when the CPU is interrupted, among other things, the hardware clears the IRQ Enable bit in the CPSR of the IRQ CPU Mode in which
- * we enter. */
- wasIRQDisabled = IS_IRQ_DISABLED();
/* Interrupt in the CPU must be turned off while the ICCPMR is being
* updated. */
@@ -505,20 +485,7 @@
"isb \n"::: "memory" );
}
- /* Just like this function returns a value of wether or not the interrupts where masked in the interrupt controller in order to avoid race condition when
- * calling its matching vPortClearInterruptMask function, we needed a 'wasIRQDisabled' variable holding the state of the IRQ Enable bit in the CPSR in order
- * to leave that bit in it's original state. Like mentioned above, hardware automatically clear the IRQEnable bit upon trapping into IRQ Mode, so the programmer
- * cannot make assumption about it's state. Very rare, but very important race condition is avoided with this when this function is called in an ISR. The race
- * condition in question was discovered when integrating tracealyzer code. Inside the function 'void vTaskSwitchContext( void )' in tasks.c, there is a macro 'traceTASK_SWITCHED_IN();'
- * which gets replaced by something when using the tracing capabilities. That macro protects some critical section with matching calls to 'ulPortSetInterruptMask'
- * and 'vPortClearInterruptMask'. At the time of calling those functions, the interrupt mask is not set in the interrupt controller, thus the only protecting barrier
- * against the CPU traping into recursive interrupt was the IRQ Enable bit in the CPSR. By not taking it into acount, the very code that protects the CPU against
- * critical section violation just enabled it to happen : A SysTick was waiting to happen, and calling 'portCPU_IRQ_ENABLE' would enable it to occur... Thus triggering a
- * switch of context while already performing a switch context. */
- if( !wasIRQDisabled )
- {
- portCPU_IRQ_ENABLE();
- }
+ portCPU_IRQ_ENABLE();
return ulReturn;
}
