Hi All, I need small clarification for multicore linux kernel Case;1 Kernel space: 1. If on two CPU's both running in kernel space and both crash at same time t. what will happen will we get two crash dumps of registers or single ? Case :2 User Space: 1. If on two CPU's both running in User space and both crash at same time t. what will happen will we get two core files, Single core with dump for both ? Thanks
Hi, Naveen 2011/2/15 naveen yadav <yad.naveen@gmail.com>
Hi All,
I need small clarification for multicore linux kernel
Case;1 Kernel space:
1. If on two CPU's both running in kernel space and both crash at same time t. what will happen will we get two crash dumps of registers or single ?
- when kernel dies in SMP environment, it needs to aquire spin_lock(die_lock) to enter die(). So the first one which get the lock earlier will handle die() first. If the kernel is still alive then the later one will enter die(). If kernel is in panic, it shutdown the other cpus and halt the system. So no one can do further jobs.
Case :2
User Space:
1. If on two CPU's both running in User space and both crash at same time t. what will happen will we get two core files, Single core with dump for both ?
Thanks
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Hi... On Tue, Feb 15, 2011 at 10:50, naveen yadav <yad.naveen@gmail.com> wrote:
Hi All,
I need small clarification for multicore linux kernel
Case;1 Kernel space:
1. If on two CPU's both running in kernel space and both crash at same time t. what will happen will we get two crash dumps of registers or single ?
I somewhat agree with Joongyu. So in the best case, you get one crash dump representing states of both CPUs. In worst case, you got none. IMO, it would always be single crash dump.....no matter how much CPUs you have...kernel AFAIK is single entity...
Case :2
User Space:
1. If on two CPU's both running in User space and both crash at same time t. what will happen will we get two core files, Single core with dump for both ?
ok, you mean both CPUs running different programs and currently in user mode? now in this case you shall have two core files. One core file represent single task process address space AFAIK. -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com
On Feb 15, 2011 3:55 AM, "Mulyadi Santosa" <mulyadi.santosa@gmail.com> wrote:
Hi...
On Tue, Feb 15, 2011 at 10:50, naveen yadav <yad.naveen@gmail.com> wrote:
Hi All,
....
User Space:
1. If on two CPU's both running in User space and both crash at same time t. what will happen will we get two core files, Single core with dump for both ?
ok, you mean both CPUs running different programs and currently in user mode? now in this case you shall have two core files. One core file represent single task process address space AFAIK.
Just to clarify that if a user mode program crashes, it will not crash the kernel. The kernel will continue to run fine. Regards Amit
-- regards,
Mulyadi Santosa Freelance Linux trainer and consultant
blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com
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Hi AMit... On Tue, Feb 15, 2011 at 18:31, Amit Dhingra <mechanicalamit@gmail.com> wrote:
Just to clarify that if a user mode program crashes, it will not crash the kernel. The kernel will continue to run fine.
Most of the times, yes....but if you take example of fuzzer application, it might crash while at the same time crashing the kernel due to zero day bug somewhere :D -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com
participants (4)
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Amit Dhingra -
Joongyu Sun -
Mulyadi Santosa -
naveen yadav