On Wed, Jun 2, 2021 at 6:10 AM Robert Kaiser <robert.kai...@hs-rm.de> wrote: > > Hi all, > > I'm working on the SOS example of the AOS course, trying to adapt code > that used to work under the non-MCS kernel to the now used MCS kernel. > > So far, this mostly works. However, I'm having problems in resuming a > thread that is blocked in an IPC Call operation. > > In simple cases where the server can reply immediately, the thread is > successfully unblocked, simply by replying to the reply object as with > the reply capability in the non-MCS kernel. However, if the server does > not respond immediately, (i.e. it leaves the calling thread in blocked > state, serves some other requests and/or notifications in the meantime, > then comes back to reply), replying to the reply object silently fails > to unblock the thread for some reason. > > In the non-MCS kernel, it was necessary in these cases to save the reply > capability in a cspace. Therefore I tried to similarly copy/move the > reply object to a thread-specific cspace slot, but that doesn't help. > > I'm sure I'm missing something very basic here. Can anybody point me to > the right direction? >
Hi, In MCS reply objects are no longer part of thread TCBs. Instead they are separate objects that can be created from kernel untyped. This means that a receiving thread needs a different reply object for each concurrent blocking thread it wants to hold. If the receiving thread uses a reply object that has a thread already blocked on it to receive a message from a new thread, the old thread's IPC operation is cancelled and it moves to inactive. So if you kept a separate reply object for each client thread and didn't share the reply objects between threads, the client threads should stop silently failing. > Best, > > Robert > > -- > Robert Kaiser > > Technische Informatik > Hochschule RheinMain > Wiesbaden Rüsselsheim > > Computer Engineering > RheinMain University of Applied Sciences > > robert.kai...@hs-rm.de > http://www.cs.hs-rm.de/~kaiser > > tel:(+49)611-9495-1292 > fax:(+49)611-9495-1210 > > Postal Address: > Robert Kaiser, Hochschule RheinMain, FB DCSM/Informatik > Unter den Eichen 5, 65195 Wiesbaden, Germany > > _______________________________________________ > Devel mailing list -- devel@sel4.systems > To unsubscribe send an email to devel-leave@sel4.systems _______________________________________________ Devel mailing list -- devel@sel4.systems To unsubscribe send an email to devel-leave@sel4.systems
