From: Ben Gras <ben@minix3.org>
Date: Wed, 12 Jun 2013 18:42:41 +0000 (+0000)
Subject: vfs: patch for unpause()/revive() race condition
X-Git-Tag: v3.3.0~921
X-Git-Url: http://zhaoyanbai.com/repos/Bv9ARM.ch08.html?a=commitdiff_plain;h=8f2749cca841af071f3110ef340cde615778eabd;p=minix.git

vfs: patch for unpause()/revive() race condition

	. unpause() and revive() can race - revive() can run during
	  a device i/o unblock, causing two sendnb()s to occur, and the
	  2nd one to fail
	. this can easily happen when a process is blocking on tty and
	  is then killed by a signal - tty cancels the i/o and then
	  kills the process by a signal

Change-Id: Ia319acaedfa336b78c030a2c4af7246959bdcf87
---

diff --git a/servers/vfs/pipe.c b/servers/vfs/pipe.c
index f9a4cfb3c..8f4fd7036 100644
--- a/servers/vfs/pipe.c
+++ b/servers/vfs/pipe.c
@@ -640,13 +640,14 @@ void unpause(endpoint_t proc_e)
 		panic("VFS: unknown block reason: %d", blocked_on);
   }
 
-  rfp->fp_blocked_on = FP_BLOCKED_ON_NONE;
-
   if ((blocked_on == FP_BLOCKED_ON_PIPE || blocked_on == FP_BLOCKED_ON_POPEN)&&
 	!wasreviving) {
 	susp_count--;
   }
 
-  replycode(proc_e, status);	/* signal interrupted call */
+  if(rfp->fp_blocked_on != FP_BLOCKED_ON_NONE) {
+	rfp->fp_blocked_on = FP_BLOCKED_ON_NONE;
+	replycode(proc_e, status);	/* signal interrupted call */
+  }
 }