On Sat, Feb 9, 2013 at 8:08 AM, Peter Teoh <htmldevelo...@gmail.com> wrote:
> > > On Sat, Feb 9, 2013 at 1:08 AM, Gaurav Jain <gjainroor...@gmail.com>wrote: > >> What happens if the kernel executing in some process context (let's say >> executing a time-consuming syscall) gets interrupted by the Timer - which >> is apparently allowed in 2.6 onwards kernels. >> >> My understanding is that once the interrupt handler is done executing, we >> should switch back to where the kernel code was executing. Specifically, >> the interrupt handler for the Timer interrupt should not schedule some >> other task since that might leave kernel data in an inconsistent state - >> kernel didn't finish doing whatever it was doing when interrupted. >> > > at the microscopic level, every stream of assembly instructions can always > be broken up and intercepted by interrupt, and possibly switched into > another stream of assembly instruction or logic, the maintenance of state > "consistency" is done via context switching. > context switching is done at software level, and i am not if there is difference between process context switch or thread/task level context switching, but hardware only guarantee register context switch - and not sure if it covers all the floating point (SSE) registers too (unlikely, performance overheads)....so.."consistency" is really how you write your software. and u also have multiple switching (by different CPU) all taking place independently all the time, writing into the same piece of RAM. I also know that nvidia GPU does not clean up its memory/state when switching from one process to another process, but that is beyond the control of hardware switching logic of the CPU anyway. > >> So, does the Timer interrupt handler include such a policy for the above >> case? >> >> -- >> Gaurav Jain >> >> >> >> >> _______________________________________________ >> Kernelnewbies mailing list >> Kernelnewbies@kernelnewbies.org >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >> >> > > > -- > Regards, > Peter Teoh -- Regards, Peter Teoh
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