Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760733AbZFXQQp (ORCPT ); Wed, 24 Jun 2009 12:16:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760560AbZFXQQh (ORCPT ); Wed, 24 Jun 2009 12:16:37 -0400 Received: from ey-out-2122.google.com ([74.125.78.25]:20845 "EHLO ey-out-2122.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751976AbZFXQQg (ORCPT ); Wed, 24 Jun 2009 12:16:36 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:from:date:message-id:subject:to:content-type :content-transfer-encoding; b=K6HloMXjRW8EciKZxtYCH8uVHRb5a1CKhi0NcjBL9GpnI2n9y/ZRNZkeWKxx/vuIRx YpOhpCjwbF3EUMxZugiGgWXYrrsGY1UpbvsC10NQhU4lXbj2/e3exVRPl62WTg5I1AX8 OsqND+l8iCM+GEqrQcD6MbsJDoU3a1dN1Nwm4= MIME-Version: 1.0 From: Bryan Donlan Date: Wed, 24 Jun 2009 12:16:18 -0400 Message-ID: <3e8340490906240916v8017770w279e7ecfab079894@mail.gmail.com> Subject: PI futexes - allocations required? To: LKML , Ingo Molnar Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 825 Lines: 15 When I was reading the futex.c code, I noticed that locking a PI mutex can apparently cause an allocation, via alloc_pi_state() and refill_pi_state_cache(). Doesn't this mean that memory allocation (and the corresponding possible IO latency) could be introduced into real-time code - the primary user of PI mutexes? Am I missing something here, or is some sort of PI mutex "prefaulting" needed to avoid allocation when taking PI locks? It would seem that the sleeps and unbounded latency that a GFP_KERNEL allocation can introduce would make these unusable for real-time code... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/