-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Eric Dumazet wrote: > 3) if condvar is PRIVATE and mutex is SHARED, a FUTEX_WAKE_PRIVATE > should be done. (and loose the REQUEUE optim) > Yes we could add a special futex primitive for this special case. But I > cannot see how a program could use such a construct.
Very easily: mutexes are often created independently from the condvars and they are used for many things. Maybe a program is even creating all mutexes as shared to be ready for all situations. Normally doing this is no big problem, the performance penalties are minimal. > 4) if condvar is SHARED and mutex is private, we have a *problem*, > because the process doing the broadcast() can be in another mm. So a > requeue is not possible at all. It is if we can specify the owner of the mutex. I.e., the PID. But yes, this case is extremely ugly. The problem is that all these cases worked nice so far. They all had the same good performance. Now we are severely penalizing code which mismatches condvar and mutex shared attributes. There is a good reason why we introduced FUTEX_CMP_REQUEUE, the benefits in certain programs is huge. - -- ➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (GNU/Linux) Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org iD8DBQFGUfZT2ijCOnn/RHQRAkT0AJ4pgX7RtdUf8uwyP9v7o+nkv/9uMACfbx6+ kBaJLSSvDBjN09KMgmLKnSI= =4XMz -----END PGP SIGNATURE----- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
