Shriramana Sharma wrote: > > When a system call is invoked, the process which has invoked is being > > interrupted and all the information needed to continue this process is > > stored for later use. Now, the process executes higher privileged > > code that determines what to do next from examining the stack of the > > less privileged code. It contains information about the request to be > > served by the kernel. When it is finished, it control is returned to > > the program, restoring the saved state and continuing program > > execution. > > So technically the kernel instructions would be processed "in" the same > process and thread that makes the system call, albeit with different > privelege, right? Or is the process *making the system call* totally > "paused", as in a "wait" situation when one process waits for another to > finish? The kernel is a completely different "process" in so far as it has a separate task descriptor, and thus a different memory layout etc. The system call is executed in the same "flow" in that the INT-80 instruction causes the CPU to start executing kernel code; after the system call has completed, control will eventually return to the calling process at the instruction after the INT-80. In that sense, it's similar to a function call, but the similarity largely stops there. -- Glynn Clements <glynn@xxxxxxxxxxxxxxxxxx> - To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
