From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesper Skov To: "Xavier Wang" Cc: Subject: Re: [ECOS] nested interrupts Date: Thu, 18 Jan 2001 01:03:00 -0000 Message-id: References: <003b01c0811f$196395e0$6f2314ac@realtek.com.tw> X-SW-Source: 2001-01/msg00300.html >>>>> "Xavier" == Xavier Wang writes: Xavier> I got confused about nested interrupts. In Xavier> http://sources.redhat.com/ecos/docs-latest/porting/hal-interrupts.html Xavier> it seems that interrupts are disabled in ISRs, but enabled in Xavier> DSRs. Xavier> But Hugo's description in the same page said that Xavier> higher priority interrupts are enabled before calling Xavier> ISR. Which is true for nested interrupts? Both are true, but depending on configuration. There is an option that allows nested interrupts - when disabled, the former is valid, when enabled, the latter is valid. Xavier> If it's the former, should I rewrite the 'hal_cpu_int_enable' Xavier> macro used in hal_interrupt_stack_call_pending_DSRs (in Xavier> vector.S) to enable only higher priority interrupts? If it's No. All interrupts are allowed when executing DSRs. DSRs are only executin when no interrupts are pending. Xavier> the latter, what should I do to support nested interrupts? Xavier> (I'm using TX39/JMR3904 platform, eCos version 1.3.1) You need code that enabled higher level interrupts depending on the state of CYGSEM_HAL_COMMON_INTERRUPTS_ALLOW_NESTING. The code needs to go either somewhere in vectors.S around the place where the hal_cpu_except_enable macro is called. I don't know if a variant/platform specific version of that macro would be a suitable solution. None of the other MIPS platforms allow nested interrupts. Xavier> Besides, by looking into the source code, it seems that if Xavier> there is any pending DSRs, no thread will be run. So can a Xavier> high priority thread be blocked by a low priority interrupt Xavier> (DSR)? Yes. Xavier> Will it introduce some problems for a real-time application? I guess that depends on how you program the DSRs/threads. But I don't have anything intelligent to say to that, so I won't. Jesper