[ECOS] ecos newbie question: the stack for interrupt_end()

["wyb" <wyb at topsec dot com dot cn>]

In arm HAL, the following code said that interrupt_end() should be called on
the thread stack.

=========================================
spurious_IRQ:
#ifdef CYGIMP_HAL_COMMON_INTERRUPTS_USE_INTERRUPT_STACK
        // If we are returning from the last nested interrupt, move back
        // to the thread stack. interrupt_end() must be called on the
        // thread stack since it potentially causes a context switch.
        ldr     r2,.irq_level
        ldr     r3,[r2]
        subs    r1,r3,#1
        str     r1,[r2]
        ldreq   sp,[sp]         // This should be the saved stack pointer
#endif
==========================================

But if the thread was in user mode, the "ldreq sp, [sp]" still loaded SP
with svc_sp,not usr_sp. because the sp saved in interrupt_stack was svc_sp.
The "ldreq sp, .__interrupt_stack" in following code saved the svc_sp. Mybe
i'm false, can anyone help me.

#ifdef CYGIMP_HAL_COMMON_INTERRUPTS_USE_INTERRUPT_STACK
        // Switch to interrupt stack
        ldr     r2,.irq_level           // current number of nested
interrupts
        ldr     r0,[r2]
        add     r1,r0,#1
        str     r1,[r2]                 // if was zero, switch stacks
        cmp     r0,#0
        moveq   r1,sp                   // save old stack pointer
        ldreq   sp,.__interrupt_stack
        stmeqfd sp!,{r1}
10:
#endif


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