Thanks Neil. I was an idiot to have overlooked that. Thanks once again Regards Suthambhara On Tue, 12 Oct 2004 07:09:09 -0400, Neil Horman <nhorman@xxxxxxxxxx> wrote: > > > suthambhara nagaraj wrote: > > Hi all, > > > > I have not understood how the common kernel stack in the > > init_thread_union(2.6 ,init_task_union in case of 2.4) works for all > > the processes which run on the same processor. The scheduling is round > > robin and yet the things on the stack (saved during SAVE_ALL) have to > > be maintained after a switch without them getting erased. I am > > familiar with only the i386 arch implementation. > > > > Please help > > > There is no such thing as "the common kernel stack". Each process > (represented by a task_struct in the kernel) has its own private data > space to be used as a kernel stack when that process traps into the > kernel. You can see where this per task_struct stack space is reserved > in the definition of task_union. init_[task|thread]_union just defines > the first task union in the system. Because of the way unions are laid > out in memory, The kernel knows that when a process traps into kernel > space, it just needs to round the current task pointer to the nearest 8k > (prehaps 4k in 2.6) boundary, and thats the start of that processes > kernel stack. Thats how the SAVE_ALL command avoids trampling registers. > > HTH > Neil > > regards, > > Suthambhara > > - > > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > Please read the FAQ at http://www.tux.org/lkml/ > > -- > /*************************************************** > *Neil Horman > *Software Engineer > *Red Hat, Inc. > *nhorman@xxxxxxxxxx > *gpg keyid: 1024D / 0x92A74FA1 > *http://pgp.mit.edu > ***************************************************/ > -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
