From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [Qemu-devel] Re: [PATCH 08/10] MCE: Relay UCR MCE to guest
Date: Wed, 20 Oct 2010 19:28:47 -0200
Message-ID: <20101020212847.GA11588@amt.cnet>
References: <cover.1287596626.git.mtosatti@redhat.com>
 <10ae5833ff9de153c311917d532f3e84e5b00387.1287596626.git.mtosatti@redhat.com>
 <4CBF485C.9060808@linux.vnet.ibm.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org,
	Avi Kivity <avi@redhat.com>
To: Anthony Liguori <aliguori@linux.vnet.ibm.com>
Return-path: <kvm-owner@vger.kernel.org>
Received: from mx1.redhat.com ([209.132.183.28]:41724 "EHLO mx1.redhat.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1752614Ab0JTVkG (ORCPT <rfc822;kvm@vger.kernel.org>);
	Wed, 20 Oct 2010 17:40:06 -0400
Content-Disposition: inline
In-Reply-To: <4CBF485C.9060808@linux.vnet.ibm.com>
Sender: kvm-owner@vger.kernel.org
List-ID: <kvm.vger.kernel.org>

On Wed, Oct 20, 2010 at 02:51:56PM -0500, Anthony Liguori wrote:
> >+        e = errno;
> >+
> >+        qemu_mutex_lock(&qemu_global_mutex);
> >+
> >+        if (r == -1&&  !(e == EAGAIN || e == EINTR)) {
> >+            fprintf(stderr, "sigtimedwait: %s\n", strerror(e));
> >+            exit(1);
> >+        }
> >+
> >+        switch (r) {
> >+        case SIGBUS:
> >+#ifdef TARGET_I386
> >+            if (kvm_on_sigbus_vcpu(env, siginfo.si_code, siginfo.si_addr))
> >+#endif
> >+                sigbus_reraise();
> >+            break;
> >+        default:
> >+            break;
> >+        }
> >+
> >+        r = sigpending(&chkset);
> >+        if (r == -1) {
> >+            fprintf(stderr, "sigpending: %s\n", strerror(e));
> >+            exit(1);
> >+        }
> >+    } while (sigismember(&chkset, SIG_IPI) || sigismember(&chkset, SIGBUS));
> >  }
> 
> I don't understand why this loop is needed but we specifically wait
> for a signal to get delivered that's either SIG_IPI or SIGBUS.  We
> then check whether a SIG_IPI or SIGBUS is pending and loop waiting
> for signals again.
>
> Shouldn't we be looping on just sigismember(SIGBUS)?

Think of SIG_IPI and SIGBUS pending. SIGBUS must be processed
immediately.

Yes, sigismember(SIGBUS) would be fine. But the current code too.

> BTW, we're no longer respecting timeout because we're not adjusting
> ts after each iteration.

Right, timeout not used at the moment.