On Sat, Jan 16, 2021 at 07:12:54AM +0200, Jarkko Sakkinen wrote: > > https://lkml.kernel.org/r/X/zoarV7gd/LNo4A@xxxxxxxxxx > > OK, I could recall the race that from but that must be partly because I've > been proactively working on it, i.e. getting your point. > > So let's say I add this after the sequence: > > "The sequence demonstrates a scenario where CPU B starts a new > grace period, which goes unnoticed by CPU A in sgx_release(), > because it did not remove the final entry from the enclave's > mm list." > > Would this be sufficient or not? Not sure. That link above says: "Now, let's imagine that there is exactly one entry in the encl->mm_list. and sgx_release() execution gets scheduled right after returning from synchronize_srcu(). With some bad luck, some process comes and removes that last entry befoe sgx_release() acquires mm_lock." So, the last entry gets removed by some other process before sgx_release() acquires mm_lock. When it does acquire that lock, the test if (list_empty(&encl->mm_list)) will be true because "some other process" has removed that last entry. So why do you need the synchronize_srcu() call when this process sees an empty mm_list already? Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette
