Messages in this thread | | | From | Keith Owens <> | Subject | Re: [RFC] Changing SysRq - show registers handling | Date | Fri, 04 Jun 2004 08:21:18 +1000 |
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On Thu, 3 Jun 2004 17:06:01 -0400, Theodore Ts'o <tytso@mit.edu> wrote: >On Thu, Jun 03, 2004 at 09:44:01AM +0200, Oliver Neukum wrote: >> Am Donnerstag, 3. Juni 2004 09:27 schrieb Dmitry Torokhov: >> > I don't like the requirement of SysRq request processing being in hard >> > interrupt handler - that excludes uinput-generated events and precludes >> > moving keyboard handling to a tasklet for example. >> >> SysRq should work even if bottom halfs don't. > >Indeed; one of the times when SysRq-p is used in the field is when the >machine is completely wedged. Sometimes it's the only way to figure >out where the machine is wedged. It would be unfortunate if the >number of cases (when the kernel is four feet in the air and >twitching) where SysRq worked decreases as a result of the proposed >change.
KDB has a similar problem, it needs struct pt_regs as a starting point for backtraces and that is not always available. I get around the lack of a pt_regs by using KDB_ENTER() which generates a software interrupt. We could define a software interrupt for SYSRQ_ENTER(key). This would remove all the overhead of saving and tracking pt_regs from the fast paths. The downside is that it needs a software interrupt to be defined for every arch :(.
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