I am new to kernel programming and have a lot questions about this structure. Also if after you guys reply I have a few \ questions for Greg Kroah Hartman about usb development and stable trees. I am very excited about learning this properly now and if anyone notices something wrong in my understanding please let me known :). Thanks So Much, Nick Questions about task_struct 1.volatile long state; Is this line like jiffies for timers with regards to the keyword volatile? 2.void *stack; Is this a pointer to the kernel stack for the process related to the process that the structure is keeping data for and is void to make it an opaque data type? Is this normally an int or some other data type when called with most processes? 3.unsigned int flags; /* per process flags, defined below */, My only question about this is what flags are there and are these the ifdef statements in the struct? 4.Why are we making the usage count atomic?(pretty obvious but real world reasons would be great) 5.I assume int ptrace is for ptrace or debugged processes? If I wrong please let me known too. 6. What is wakkee_flips and wakkee_flips_decay used for? 7.This is probably a stupid question but are these the scheduler cases for CFS? 1240 int on_rq; 1241 1242 int prio, static_prio, normal_prio; 1243 unsigned int rt_priority; 1244 const struct sched_class *sched_class; 1245 struct sched_entity se; 1246 struct sched_rt_entity rt; 1247 #ifdef CONFIG_CGROUP_SCHED 1248 struct task_group *sched_task_group; 1249 #endif 1250 struct sched_dl_entity dl; 8.What are preempt notifiers and what are they for?(another stupid question) 9. Are these lines for the policy used and to block certain processes to only a few processors? 1261 unsigned int policy; 1262 int nr_cpus_allowed; 1263 cpumask_t cpus_allowed; 8.What are the options like CONFIG_PREEMPT_RCU used for in terms of workloads or locking as I heard a lot about them on the threads on the lkml? P.S. Sorry about some many questions,. Answer then whenever you guys have time and if there stupid and easily found somewhere let me known.