From: Khalid Aziz <khalid.aziz@xxxxxxxxxx> Date: Wed, 30 Aug 2017 17:23:37 -0600 > That is an interesting idea. This would enable TSTATE_MCDE on all > threads of a process as soon as one thread enables it. If we consider > the case where the parent creates a shared memory area and spawns a > bunch of threads. These threads access the shared memory without ADI > enabled. Now one of the threads decides to enable ADI on the shared > memory. As soon as it does that, we enable TSTATE_MCDE across all > threads and since threads are all using the same TTE for the shared > memory, every thread becomes subject to ADI verification. If one of > the other threads was in the middle of accessing the shared memory, it > will get a sigsegv. If we did not enable TSTATE_MCDE across all > threads, it could have continued execution without fault. In other > words, updating TSTATE_MCDE across all threads will eliminate the > option of running some threads with ADI enabled and some not while > accessing the same shared memory. This could be necessary at least for > short periods of time before threads can communicate with each other > and all switch to accessing shared memory with ADI enabled using same > tag. Does that sound like a valid use case or am I off in the weeds > here? A threaded application needs to synchronize and properly orchestrate access to shared memory. When a change is made to a mappping, in this case setting ADI attributes, it's being done for the address space not the thread. And the address space is shared amongst threads. Therefore ADI is not really a per-thread property but rather a per-address-space property. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
