Messages in this thread Patch in this message |  | | Subject | Re: Question about rtc_lock | From | Thomas Hood <> | Date | 06 Oct 2001 23:24:02 -0400 |
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On Sat, 2001-10-06 at 11:24, Jonathan Lundell wrote: > rtc_interrupt(), you mean.
Right.
> Even if there weren't current interrupt code doing CMOS accesses, it > would seem prudent to assume that there might be eventually, the > RTC/NVRAM being a multi-purpose shared resource.
I'm not concerned about an irq handler (present or future) interfering with us as we write to the CMOS RAM. What I'm concerned about is getting a rtc interrupt while we hold rtc_lock, with deadlock being the result (since rtc_interrupt will spin on the lock).
Either (1) we need to change these spinlocks to _irq, or (2) we need to know that this bit of code runs only with irqs disabled. My question is: Is it (1) or (2)?
Or is it (3) Thomas Hood is failing to understand something here?
Assuming the answer is (1), I append a patch that changes the spinlock calls to _irqsave versions.
Cheers, Thomas
The patch: --- linux-2.4.10-ac5-fix/arch/i386/kernel/bootflag.c_PREV Fri Oct 5 23:20:43 2001 +++ linux-2.4.10-ac5-fix/arch/i386/kernel/bootflag.c Sat Oct 6 23:15:33 2001 @@ -81,26 +81,30 @@ static void __init sbf_write(u8 v) { + unsigned long flags; + if(sbf_port != -1) { v &= ~(1<<7); if(!parity(v)) v|=1<<7; - spin_lock(&rtc_lock); + spin_lock_irqsave(&rtc_lock, flags); CMOS_WRITE(v, sbf_port); - spin_unlock(&rtc_lock); + spin_unlock_irqrestore(&rtc_lock, flags); } } static u8 __init sbf_read(void) { u8 v; + unsigned long flags; + if(sbf_port == -1) return 0; - spin_lock(&rtc_lock); + spin_lock_irqsave(&rtc_lock, flags); v = CMOS_READ(sbf_port); - spin_unlock(&rtc_lock); + spin_unlock_irqrestore(&rtc_lock, flags); return v; } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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