Hi, As you stated below I saw SET_LINKS in sched.h file and everything makes sense. I did not know that the parents processes children member points to the childs sibling member. I thought it pointed to the children member of the child and that is where I went wrong. Thanks Vish --- Mulyadi Santosa <mulyadi.santosa@xxxxxxxxx> wrote: > Hello..... > > > From what I understand, list_for_each above will > > iterate through one of the current processes child > (if > > there was one), then that childs child(if there is > > one) and so on. Am I right in concluding this? > This > > means only the first iteration will find the > current > > processes child. > > No. The codes you read are simply iterating on all > children of a certain > task. So, if process A is forking process B,C and D, > the snippets will > iterate from B to D, but not the children of B, C or > D :) > > > linux/kernel.h, task cannot point to the > task_struct > > of the child because list_entry subtracts the > offset > > of sibling member from the address of the children > > member. This will subtract more than is necessary. > So, > > the first argument of list_entry should point to a > > list head member with the same member name within > the > > struct. Otherwise it will not return the address > of > > the containing struct. Am I right in concluding > this? > > I don't understand your question clearly, but I > assume that you have > doubt about whether is it correct to use "list" as > first argument for > list_entry(), am I correct? > > recall the fact that "list" is actually a pointer > pointing to each node > of current->children's linked list. "list" itself > won't give any clue > because it can be anything which is declared as > list_head. > > that's why you need third argument, that is > "sibling". Since "sibling" > is the pointer which points to the parent's > children, this is the one > you need. In other word, "sibling" is the list_head > you are looking > for. > > For better insight why it works, see copy_process() > on kernel/fork.c and > pay attention when it calls SET_LINKS (see > include/linux/sched.h). > > > From what I understand browsing through the kernel > > source, the only way to iterate through a > processes > > children is by asking a child to iterate through > its > > siblings. Am I right? > > IIRC, that is another solution you can pick. > > regards > > Mulyadi > > __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
