Messages in this thread | | | Date | Thu, 03 Jun 2004 00:03:04 -0700 | From | Andy Lutomirski <> | Subject | Re: [RFC] Changing SysRq - show registers handling |
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Dmitry Torokhov wrote:
> Hi, > > Currently SysRq "show registers" command dumps registers and the call > trace from keyboard interrupt context when SysRq-P. For that struct pt_regs * > has to be dragged throughout entire input and USB systems. Other than passing > this pointer to SysRq handler these systems has no interest in it, it is > completely foreign piece of data for them and I would like to get rid of it. > > I am suggesting slightly changing semantics of SysRq-P handling - instread > of dumping registers and call trace immediately it will simply post a request > for this information to be dumped. When next HW interrupt arrives and is > handled, before running softirqs then current stack trace will be printed. > This approach adds small overhead to the HW interrupt handling routine as the > condition has to be checked with every interrupt but I expect it to be > negligible as it is only check and conditional jump that is almost never > taken. The code should be hot in cache so branch prediction should work just > fine.
What about checking the flag on return from the input interrupts? That way the overhead would be confined to code paths take the hit from passing an extra parameter.
> > The patch below implements proposed changes in SysRq handler and adds > necessary changes to do_IRQ() on i386. If it is agreed upon I will adjust > other arches. > > Please let me know what you think. >
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