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Jump label reworked

Jump label reworked

Posted Mar 31, 2011 13:25 UTC (Thu) by jwessel (guest, #63702)
Parent article: Jump label reworked

This is great news that this has a possibility of being merged.

At the point in time this is merged it opens the door for fixing a long standing problem with the kernel debugger which you can only change today at kernel compilation time. The problem is that of keeping the debugger out of any kind of hot or default path while not in use.

The prime example on x86 is in the trap code. To avoid the possibility of recursive faults in any notification code, all traps need to pass through the kernel debug core first. Today you turn on CONFIG_KGDB_LOW_LEVEL_TRAP or you could choose to "use the debugger _very_ carefully". The jump label interface would allow us to easily turn this behavior on and off based on if an end user turn on the kernel debugger at runtime.

If you take this a step further it might also be plausible to solve the age old problem of who gets called first when killing a system, kexec or the debugger because you cannot use a notifier in the hard fail path for reliability issues. Today you change the oops handler, or unconfigure kexec if you want the debugger (kgdb or kdb) to get called first.

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