Hi Robert Thanks for the info.. i was under an idea that software interrupts can be used to send some kind of signals to the user space asynchronously. Is it possible for a driver running in the kernel to generate a software interrupt asynchronously to the user such that the user is informed of some change in the kernel the driver is involved with? I am well aware of the fasync method of asynchronous notification..but want to know if this way of signalling is feasible or not? Regards, Vijay Ram.C On Fri, 15 Jul 2005, Thomas Petazzoni wrote: > Hello, > > Vijay Ram Chitrapu (RCVIJAYD) wrote: > > > Can anyone help me understand what Software Interrupts are? > > Any links or examples are welcomed.. > > Basically, on x86 architecture, you can have three sources of interruption : > > - the processor himself, that generates "exceptions", such as Page > Fault, General Protection Fault, Divide by Zero and so on. On IA32 > architecture, there are 32 exceptions ; > > - the hardware, such as network cards, sound cards, hard drives and > much more generates IRQs to signal an event (arrival of a network > packet, acknowledgment of a DMA transfer, etc.) ; > > - the software which, using the «int» instruction, explicitly > generates a so-called «software interrupt». > > So, the software interrupts are interrupts that are generated explicitly > by the code running on the processor. The typical usage of such > interrupts is to implement syscalls : when the code is running in user > (non privileged) mode, it cannot call kernel code directly. In order to > switch to kernel (privileged) mode, a software interrupt is used (at > least on x86). > > Don't hesitate to ask for more details. Others, don't hesitate to > correct me if I'm wrong. > > Sincerly, > > Thomas > -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
