On Fri, May 27, 2011 at 2:44 PM, Naman shekhar Mishra <namanshekharmishra2@xxxxxxxx> wrote: > In Operating System Concepts 6th ed, chapter 20: > "Kernel code can thus assume that it will never be preempted by another > process and that no special care must be > taken to protect critical sections. The only requirement is that critical > sections do not contain references to user memory > or waits for I/O completions" This is available only if the kernel is non-preemptive. If the kernel is preemptive than a process executing in kernel, can be preempted by another process. > Why us that the process cannot wait for I/O to complete in critical > sections? Because deadlocks may sneak in ([1]). > My another question is: While developing kernel modules (for kernels before > 2.6), do we need to keep concurrency in mind? I guess yes. Even if the kernel is non-preemptive, you may want to consider SMP. > Because the modules run as part of the kernel and no two processes can run > in the kernel at the same time? Or my question is wrong since they CAN run > in the kernel at the same time (like when one process waits for I/O > completion and another is scheduled to run which then makes a system call)? > > Please excuse me for the multiple nested question since I didn't quite know > how to put it. HTH, Daniel. [1] https://lwn.net/Articles/274695/ _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
