Messages in this thread | | | From | Dmitry Torokhov <> | Subject | Re: [RFC] Changing SysRq - show registers handling | Date | Thu, 3 Jun 2004 02:15:04 -0500 |
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On Thursday 03 June 2004 02:03 am, Andy Lutomirski wrote: > > 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. >
It is hard to define what input interrupt is - PS/2 keyboard in KBD port (IRQ 1), PS/2 keyboard in AUX port (IRQ 12), USB, serial port, parralel port keyboard adapter... and all other achitectures taht have their means - it's impossible to track them all.
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