On 9/8/05, Roy Smith <misterdabolina@xxxxxxxxx> wrote: > > here's the deal. I'm acquinted with locking issues in the userland. the > problem > that is attacking me lately regards kernel code only: let's say I'm handling > data that can be accessed *ONLY* by one thread of execution, which happens > to be a kernel module. normaly, in userland, i would not have to worry about > locking - no other thread of execution have access to the data, and my code > can be executed ONLY by one processor, no matter what. now let's move > to the kernel dimension. here, the same code is run concurrently on every > processor - > we are not talking about a task which resides on a specific runqueue list, > and is attached to a certain processor. so when my kernel module gets to > run, it is not attached to any specific processor, and it might even run > in parallel on two or more processors, so even local variables now seems > to demand locking. > where am I wrong here ? > First think in terms that module is nothing but a way of adding some new funcitonality with-in the kernel .... so when you load the module it just calls your init_module function (in which you register things with kernel, mentioning the stuffs for your funcitonalities added to the kernel, and you might creates threads/process which starts doing something you need) and then module entry remains in the kernel only till module unloading time ..... after loading module your functionalities are now in the kernel ..... they can be callbacked by the kernel due to system call, /proc interface etc if you registered those with kernel and your threads/process might be running tooo if u created them .... Ad far as thread is concerned, if you have some data structure/variable and that is used only by one thread then I think it will run only on the single processor at a time, so don't need locking in that case ........ by the way thread might be preempted and then later continue on the other processor but remain running on a single processor at a single time .... (CMIIW) But plzz be specific abt what you want to do and your module is doing ..... -- Fawad Lateef -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
