[RFC] adding --sync option to udevsettle

[Thierry Vignaud <tvignaud@mandriva.com>]

[-- Attachment #1: Type: text/plain, Size: 993 bytes --]

(First, note that I'm *NOT* subscribe to this ml, so please keep in
Cc: when answering)

Hi,

While using diskdrake on a system with udev, I found out that when
resizing a partition, when we rewrite it and tell the kernel about the
new partitions sizes, there's a race window with udev which then
delete and recreate the nodes.

I think this can happen with quite a lot of tools that have to deal
with /dev/ nodes and happens to make one being indectly created by
doing sg with the kernel (creating a network interface, loading a mass
storage driver, ...).

OK, there's the udevsettle solution.

But it's not complete.

Eg: here we want to wait that device nodes were created in /dev (aka
really a sync in the command queue by analogy with disks controlling),
we do not want to wait for further commands.

The following patch add the --sync option that enables to alter
udevsettle behavior not to wait for further events to be processed (in
case somebody is hapilly feeding udev with events):

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: udevsettle.diff --]
[-- Type: text/x-patch, Size: 1092 bytes --]

--- ./udevsettle.c.tv	2007-05-16 16:33:34.000000000 +0200
+++ ./udevsettle.c	2007-05-16 16:39:04.000000000 +0200
@@ -62,6 +62,8 @@
 	int loop;
 	int i;
 	int rc = 1;
+	int sync_mode = 0;
+	int read_done = 0;
 
 	logging_init("udevsettle");
 	udev_config_init();
@@ -84,6 +86,8 @@
 		} else if (strcmp(arg, "--help") == 0 || strcmp(arg, "-h") == 0) {
 			printf("Usage: udevsettle [--help] [--timeout=<seconds>]\n");
 			goto exit;
+		} else if (strncmp(arg, "--sync", 6) == 0) {
+				sync_mode = 1;
 		} else {
 			fprintf(stderr, "unrecognized option '%s'\n", arg);
 			err("unrecognized option '%s'\n", arg);
@@ -111,6 +115,8 @@
 		}
 
 		/* read current udev seqnum */
+		if (sync_mode && !read_done) {
+						read_done = 1;
 		strlcpy(filename, udev_root, sizeof(filename));
 		strlcat(filename, "/" EVENT_SEQNUM, sizeof(filename));
 		fd = open(filename, O_RDONLY);
@@ -123,6 +128,7 @@
 		seqnum[len] = '\0';
 		seq_udev = strtoull(seqnum, NULL, 10);
 		info("udev seqnum = %llu", seq_udev);
+		}
 
 		/* read current kernel seqnum */
 		strlcpy(filename, sysfs_path, sizeof(filename));

[-- Attachment #3: Type: text/plain, Size: 208 bytes --]


What do you think?
Will you include it?

Note that I'ven't reindented the code in the new "if { ... }" block
for readibility but I can send another patch to bring indent in sync
with logical flow.


See you

[-- Attachment #4: Type: text/plain, Size: 286 bytes --]

-------------------------------------------------------------------------
This SF.net email is sponsored by DB2 Express
Download DB2 Express C - the FREE version of DB2 express and take
control of your XML. No limits. Just data. Click to get it now.
http://sourceforge.net/powerbar/db2/

[-- Attachment #5: Type: text/plain, Size: 226 bytes --]

_______________________________________________
Linux-hotplug-devel mailing list  http://linux-hotplug.sourceforge.net
Linux-hotplug-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel