File 0021-linux-user-Run-multi-threaded-code-.patch of Package qemu

Overview Repositories Revisions Requests Users Attributes Meta

File 0021-linux-user-Run-multi-threaded-code-.patch of Package qemu (Revision 9c05396d31a8a85fcedb12dfa53d980b)

Currently displaying revision 9c05396d31a8a85fcedb12dfa53d980b , Show latest

From e08016b4b3af23f8d796bf0adf258670bc92a5da 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 689bd33..38cee23 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -4434,6 +4434,15 @@ 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);

Places

File 0021-linux-user-Run-multi-threaded-code-.patch of Package qemu (Revision 9c05396d31a8a85fcedb12dfa53d980b)

Places