Linux Kernel 2.4 Internals Linux Kernel 2.4 Internals Table of Contents Linux Kernel 2.4 Internals.................................................................................................................................1 Tigran Aivazian tigran@veritas.com.......................................................................................................1 1. Booting.................................................................................................................................................1 2. Process and Interrupt Management......................................................................................................1 3. Virtual Filesystem (VFS).....................................................................................................................2 4. Linux Page Cache................................................................................................................................2 5. IPC mechanisms..................................................................................................................................2 1. Booting.................................................................................................................................................2 1.1 Building the Linux Kernel Image......................................................................................................2 1.2 Booting: Overview.............................................................................................................................3 1.3 Booting: BIOS POST.........................................................................................................................4 1.4 Booting: bootsector and setup............................................................................................................4 1.5 Using LILO as a bootloader...............................................................................................................7 1.6 High level initialisation......................................................................................................................7 1.7 SMP Bootup on x86...........................................................................................................................9 1.8 Freeing initialisation data and code...................................................................................................9 1.9 Processing kernel command line.....................................................................................................10 2. Process and Interrupt Management....................................................................................................11 2.1 Task Structure and Process Table....................................................................................................11 2.2 Creation and termination of tasks and kernel threads......................................................................15 2.3 Linux Scheduler...............................................................................................................................17 2.4 Linux linked list implementation.....................................................................................................19 2.5 Wait Queues.....................................................................................................................................21 2.6 Kernel Timers..................................................................................................................................23 2.7 Bottom Halves.................................................................................................................................23 2.8 Task Queues.....................................................................................................................................24 2.9 Tasklets............................................................................................................................................25 2.10 Softirqs...........................................................................................................................................25 2.11 How System Calls Are Implemented on i386 Architecture?.........................................................25 2.12 Atomic Operations.........................................................................................................................26 2.13 Spinlocks, Read−write Spinlocks and Big−Reader Spinlocks......................................................27 2.14 Semaphores and read/write Semaphores.......................................................................................29 2.15 Kernel Support for Loading Modules............................................................................................30 3. Virtual Filesystem (VFS)...................................................................................................................33 3.1 Inode Caches and Interaction with Dcache......................................................................................33 3.2 Filesystem Registration/Unregistration...........................................................................................36 3.3 File Descriptor Management............................................................................................................38 3.4 File Structure Management..............................................................................................................39 3.5 Superblock and Mountpoint Management.......................................................................................42 3.6 Example Virtual Filesystem: pipefs.................................................................................................45 3.7 Example Disk Filesystem: BFS.......................................................................................................47 3.8 Execution Domains and Binary Formats.........................................................................................48 4. Linux Page Cache..............................................................................................................................50 5. IPC mechanisms................................................................................................................................52 5.1 Semaphores.....................................................................................................................................52 Semaphore System Call Interfaces.................................................................................................53 sys_semget()...................................................................................................................................53 sys_semctl()....................................................................................................................................53 i Linux Kernel 2.4 Internals Table of Contents Linux Kernel 2.4 Internals sys_semop().............................................................................................................................53 Non−blocking Semaphore Operations...........................................................................................53 Failing Semaphore Operations.......................................................................................................54 Blocking Semaphore Operations....................................................................................................54 Semaphore Specific Support Structures.........................................................................................55 struct sem_array.............................................................................................................................55 struct sem........................................................................................................................................55 struct seminfo.................................................................................................................................55 struct semid64_ds...........................................................................................................................55 struct sem_queue............................................................................................................................56 struct sembuf..................................................................................................................................56 struct sem_undo..............................................................................................................................56 Semaphore Support Functions........................................................................................................56 newary()..........................................................................................................................................57 freeary()..........................................................................................................................................57 semctl_down()................................................................................................................................57 IPC_RMID.....................................................................................................................................57 IPC_SET.........................................................................................................................................57 semctl_nolock()..............................................................................................................................58