On 1/28/16, Thomas Gleixner <t...@linutronix.de> wrote: > On Thu, 28 Jan 2016, Jeffrey Merkey wrote: > >> This patch series adds an export which can be set by system debuggers to >> direct the hard lockup and soft lockup detector to trigger a breakpoint >> exception and enter a debugger if one is active. It is assumed that if >> someone sets this variable, then an breakpoint handler of some sort will >> be actively loaded or registered via the notify die handler chain. >> >> This addition is extremely useful for debugging hard and soft lockups >> real time and quickly from a console debugger. > > Why do we need an extra breakpoint instruction in the code to enter a > debugger? Don't have debuggers mechanisms to install breakpoints? > > I'm probably missing something obvious here. > > Thanks, > > tglx > > >
It's a pain in the butt to grep around through assembly language in a function in watchdog.c that has everything declared static with no symbols. It's a lot easier just to insert an INT3 in the section of code that has the mouse caught in the trap (inside a function that triggers the hard lockup) -- after all -- that's what the instruction is for. Jeff
