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qemu/0020-linux-user-Run-multi-threaded-code-.patch
Andreas Färber b6f516049c Accepting request 221154 from home:a_faerber:branches:Virtualization
Add xen_disk discard support (olh), backport VMDK SCSI change from v1.6.2 maintenance update and update syscall numbers

OBS-URL: https://build.opensuse.org/request/show/221154
OBS-URL: https://build.opensuse.org/package/show/Virtualization/qemu?expand=0&rev=179
2014-02-06 16:09:22 +00:00

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From 3a04f59b72a44bf044da642999ed16c340647809 Mon Sep 17 00:00:00 2001
From: Alexander Graf <agraf@suse.de>
Date: Tue, 10 Jul 2012 20:40:55 +0200
Subject: [PATCH] linux-user: Run multi-threaded code on a single core
Running multi-threaded code can easily expose some of the fundamental
breakages in QEMU's design. It's just not a well supported scenario.
So if we pin the whole process to a single host CPU, we guarantee that
we will never have concurrent memory access actually happen. We can still
get scheduled away at any time, so it's no complete guarantee, but apparently
it reduces the odds well enough to get my test cases to pass.
This gets Java 1.7 working for me again on my test box.
Signed-off-by: Alexander Graf <agraf@suse.de>
---
linux-user/syscall.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 5113d22..7be6873 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -4432,6 +4432,15 @@ static int do_fork(CPUArchState *env, unsigned int flags, abi_ulong newsp,
if (nptl_flags & CLONE_SETTLS)
cpu_set_tls (new_env, newtls);
+ /* agraf: Pin ourselves to a single CPU when running multi-threaded.
+ This turned out to improve stability for me. */
+ {
+ cpu_set_t mask;
+ CPU_ZERO(&mask);
+ CPU_SET(0, &mask);
+ sched_setaffinity(0, sizeof(mask), &mask);
+ }
+
/* Grab a mutex so that thread setup appears atomic. */
pthread_mutex_lock(&clone_lock);