daemonize() function is generally used to convert ordinary processes into kernel threads - like kswapd, ksoftirqd etc - which do not have an associated user-space (mm_struct). These kernel threads execute completely in kernel-space. For processes like this check out the /proc/<pid>/maps file - it will be empty - since they have no associated mm_struct. The daemonize() function reduces the reference count of the struct_mm structure by calling exit_mm(). Note: kswapd, ksoftirqd etc are especially coded for such a switch into the kernel, do NOT assume that an ordinary process can be converted into a kernel thread by calling the daemonize() through a system call or whatever. An interesting fact about kernel threads is that since, they do NOT have access to user space, they dont need the user space page-tables. So, during a process switch, the TLB (Translation Lookaside Buffer) of the previous process is not flushed (flushing is a costly operation). This concept is called Lazy TLB Flushing. On 7/25/05, NAHieu <nahieu@xxxxxxxxx> wrote: > Hello, > > Anybody here could tell me what is the purpose of daemonize() function > in kernel? In wich case should we use it? > > Thank you, > NAH > > -- > Kernelnewbies: Help each other learn about the Linux kernel. > Archive: http://mail.nl.linux.org/kernelnewbies/ > FAQ: http://kernelnewbies.org/faq/ > > -- The difference between Theory and Practice is more so in Practice than in Theory. -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
