Revert "Fix race condition when tracing is enabled (#95)" (#149)

This reverts commit 61635d5b8b.

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 @@ void vPortClearInterruptMask( uint32_t ulNewMaskValue )
 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 @@ uint32_t ulPortSetInterruptMask( void )
                          "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;
 }