[zaptel-commits] tilghman: trunk r1469 - in /trunk: ./ zaptel.c

[zaptel-commits at lists.digium.com]

Author: tilghman
Date: Sat Sep 16 02:48:33 2006
New Revision: 1469

URL: http://svn.digium.com/view/zaptel?rev=1469&view=rev
Log:
Merged revisions 1468 via svnmerge from 
https://origsvn.digium.com/svn/zaptel/branches/1.2

........
r1468 | tilghman | 2006-09-16 02:45:04 -0500 (Sat, 16 Sep 2006) | 4 lines

Round two of the fix for "hard-safe -> hard-unsafe lock order detected" (Issue 7620)
Only difference is that the fix is only defined for kernel versions 2.6.11 and
above; older kernels keep the current (possible deadlocking) code.

........

Modified:
    trunk/   (props changed)
    trunk/zaptel.c

Propchange: trunk/
------------------------------------------------------------------------------
Binary property 'branch-1.2-merged' - no diff available.

Modified: trunk/zaptel.c
URL: http://svn.digium.com/view/zaptel/trunk/zaptel.c?rev=1469&r1=1468&r2=1469&view=diff
==============================================================================
--- trunk/zaptel.c (original)
+++ trunk/zaptel.c Sat Sep 16 02:48:33 2006
@@ -1154,8 +1154,21 @@
 	/* Assumes channel is already locked */
 	if ((zone >= ZT_TONE_ZONE_MAX) || (zone < -1))
 		return -EINVAL;
-	
+
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,11)
+	/* Since this routine is called both from IRQ as well as from userspace,
+	 * it is possible that we could be called during an IRQ while userspace
+	 * has locked this.  However unlikely, this could possibly cause a
+	 * deadlock. */
+	if (! read_trylock(&zone_lock))
+		return -EWOULDBLOCK;
+#else
+	/* But there are no trylock macros for kernel versions before 2.6.11,
+	 * so we do the unsafe thing anyway.  Such is the problem for dealing
+	 * with old, buggy kernels. */
 	read_lock(&zone_lock);
+#endif
+
 	if (zone == -1) {
 		zone = default_zone;
 	}
@@ -1166,7 +1179,7 @@
 	} else {
 		res = -ENODATA;
 	}
-	
+
 	read_unlock(&zone_lock);
 	return res;
 }