From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:49659) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RGvKj-0004zF-Gi for qemu-devel@nongnu.org; Thu, 20 Oct 2011 12:19:06 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RGvKg-0003O1-PG for qemu-devel@nongnu.org; Thu, 20 Oct 2011 12:19:04 -0400 Received: from e23smtp06.au.ibm.com ([202.81.31.148]:57084) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RGvKg-0003NR-4x for qemu-devel@nongnu.org; Thu, 20 Oct 2011 12:19:02 -0400 Received: from d23relay03.au.ibm.com (d23relay03.au.ibm.com [202.81.31.245]) by e23smtp06.au.ibm.com (8.14.4/8.13.1) with ESMTP id p9KGHkKK004134 for ; Fri, 21 Oct 2011 03:17:46 +1100 Received: from d23av01.au.ibm.com (d23av01.au.ibm.com [9.190.234.96]) by d23relay03.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p9KGJ0Kg2252800 for ; Fri, 21 Oct 2011 03:19:00 +1100 Received: from d23av01.au.ibm.com (loopback [127.0.0.1]) by d23av01.au.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p9KGJ09M023118 for ; Fri, 21 Oct 2011 03:19:00 +1100 From: "Aneesh Kumar K.V" Date: Thu, 20 Oct 2011 21:47:39 +0530 Message-Id: <1319127460-5181-8-git-send-email-aneesh.kumar@linux.vnet.ibm.com> In-Reply-To: <1319127460-5181-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> References: <1319127460-5181-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Subject: [Qemu-devel] [PATCH 7/8] qemu-queue: Introduce QLIST_INSERT_HEAD_RCU and dummy RCU wrappers. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: aliguori@us.ibm.com, Harsh Prateek Bora , "Aneesh Kumar K.V" From: Harsh Prateek Bora SynthFS needs a QLIST_INSERT_HEAD_RCU to make sure list instructions are not re-ordered and therefore avoiding a crash. There may be parallel readers which should be allowed for lock-free access and this variant allows us to get rid of rwlocks used by readers. SynthFS is a special case where we dont really need full RCU capabilities as it doesnt allow list entry deletion but concurrent readers/writers and instruction re-ordering should not result in a crash. Also, once the real rcu is available, dummy rcu macro definitions will go away and the code will still work as expected. This patchwork is based on inputs from Paolo Bonzini. Signed-off-by: Harsh Prateek Bora Signed-off-by: Aneesh Kumar K.V --- qemu-queue.h | 13 +++++++++++++ qemu-thread.h | 3 +++ 2 files changed, 16 insertions(+), 0 deletions(-) diff --git a/qemu-queue.h b/qemu-queue.h index 1d07745..2214230 100644 --- a/qemu-queue.h +++ b/qemu-queue.h @@ -76,6 +76,8 @@ * For details on the use of these macros, see the queue(3) manual page. */ +#include "qemu-barrier.h" /* for smp_wmb() */ + /* * List definitions. */ @@ -122,6 +124,17 @@ struct { \ (elm)->field.le_prev = &(head)->lh_first; \ } while (/*CONSTCOND*/0) +#define QLIST_INSERT_HEAD_RCU(head, elm, field) do { \ + (elm)->field.le_prev = &(head)->lh_first; \ + (elm)->field.le_next = (head)->lh_first; \ + smp_wmb(); /* fill elm before linking it */ \ + if ((head)->lh_first != NULL) { \ + (head)->lh_first->field.le_prev = &(elm)->field.le_next; \ + } \ + (head)->lh_first = (elm); \ + smp_wmb(); \ +} while (/* CONSTCOND*/0) + #define QLIST_REMOVE(elm, field) do { \ if ((elm)->field.le_next != NULL) \ (elm)->field.le_next->field.le_prev = \ diff --git a/qemu-thread.h b/qemu-thread.h index 0a73d50..e008b60 100644 --- a/qemu-thread.h +++ b/qemu-thread.h @@ -19,6 +19,9 @@ void qemu_mutex_lock(QemuMutex *mutex); int qemu_mutex_trylock(QemuMutex *mutex); void qemu_mutex_unlock(QemuMutex *mutex); +#define rcu_read_lock() do { } while (0) +#define rcu_read_unlock() do { } while (0) + void qemu_cond_init(QemuCond *cond); void qemu_cond_destroy(QemuCond *cond); -- 1.7.5.4