On Tue, Nov 14, 2017 at 02:52:06PM -0200, Bruno E. O. Meneguele wrote: > On 26-10, Tobin C. Harding wrote: > > Is there any 'non-process' context apart from interrupt context? I had a > > re-read of sleep sections in ldd3 and in Robert Love's book but am still > > not totally clear on this. > > > > The reason for the question is understanding when we cannot sleep. > > Well, AFAIK you can simplify things to interrupt vs process context, but > you might be aware that inside interrupt context there are others (NMI, > HWIRQ, SOFTIRQ, ..), infos that you can find in Robert's book. What > confused me for sometime was the 'atomic' vs 'interrupt' naming, but > after reading Robert's book it cames to the fact that they're the same. > > The general rule is that in any interrupt context you can't sleep, and > why is that? Because interrupts aren't processes, there isn't an actual > process that the scheduler can put to sleep and wake it up later. It's > basically a design decision. Kernel-RT patches provide the feature of > sleepable interrupts, since the goal there is the latency and not > performance. That said, in short, the idea in Linux Kernel (I'm not an > expert, far from that actually, so anyone can correct me) is to make > interrupts atomic in behalf of simplicity and performance. > > But hey, be careful, there are that talk about top vs bottom halves > mechanisms (to defer work) right? Top are always in interrupt context, > but bottom ones can run in process context. The most basic ones are > Softirqs, Tasklets and Workqueues, the former is the most low-level > available and I won't talk about it, but basicaly softirqs and tasklets > run in interrupt context, thus can't sleep, while workqueues is handled > in process context, thus can sleep normally (it can be rescheduled). > > But as I said, I'm far from expert in the subject. What I've said here > is just what I know about :) > > Hope it helps you. thanks for your response, Tobin.
Attachment:
signature.asc
Description: PGP signature
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
