Re: [lxc-devel] [PATCH 1/2]: Ensure freezer state has changed

[Daniel Lezcano]

On 07/15/2010 02:59 AM, Matt Helsley wrote:
 On Fri, Jul 09, 2010 at 07:51:32PM -0700, Sukadev Bhattiprolu wrote:

 From: Sukadev Bhattiprolusuka...@linux.vnet.ibm.com
 Subject: [PATCH 1/2] Ensure frezer state has changed

 A write to the freezer.state file does not gurantee that the state has
 changed. To ensure that the freezer state is either FROZEN or THAWED,
 read the freezer state and if it has not changed, repeat the write.

 Technically this is only necessary for the THAWED -  FROZEN
 transition. In other words, if we're FROZEN and write THAWED then
 we don't need to read the state. However, it doesn't hurt to check.

 Reviewed-by: Matt Helsleymatth...@us.ibm.com

Thanks Matt for the comments.
Suka, I pushed your patch, but if you have time, that would be nice if 
you can address Matt's comments.

Thanks
   -- Daniel

--
This SF.net email is sponsored by Sprint
What will you do first with EVO, the first 4G phone?
Visit sprint.com/first -- http://p.sf.net/sfu/sprint-com-first
___
Lxc-devel mailing list
Lxc-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/lxc-devel

[lxc-devel] [PATCH 1/2]: Ensure freezer state has changed

[Sukadev Bhattiprolu]

From: Sukadev Bhattiprolu suka...@linux.vnet.ibm.com
Subject: [PATCH 1/2] Ensure frezer state has changed

A write to the freezer.state file does not gurantee that the state has
changed. To ensure that the freezer state is either FROZEN or THAWED,
read the freezer state and if it has not changed, repeat the write.

Changelog[v2]:
- Minor reorg of code
- Comments from Daniel Lezcano:
- lseek() before each read/write of freezer.state
- Have lxc_freeze_unfreeze() return -1 on error

Signed-off-by: Sukadev Bhattiprolu suka...@linux.vnet.ibm.com
---
 src/lxc/freezer.c |   50 +++---
 1 files changed, 43 insertions(+), 7 deletions(-)

diff --git a/src/lxc/freezer.c b/src/lxc/freezer.c
index cff954e..d144f89 100644
--- a/src/lxc/freezer.c
+++ b/src/lxc/freezer.c
@@ -42,6 +42,7 @@ static int freeze_unfreeze(const char *name, int freeze)
 {
char *nsgroup;
char freezer[MAXPATHLEN], *f;
+   char tmpf[32];
int fd, ret;

ret = lxc_cgroup_path_get(nsgroup, name);
@@ -50,7 +51,7 @@ static int freeze_unfreeze(const char *name, int freeze)
 
snprintf(freezer, MAXPATHLEN, %s/freezer.state, nsgroup);
 
-   fd = open(freezer, O_WRONLY);
+   fd = open(freezer, O_RDWR);
if (fd  0) {
SYSERROR(failed to open freezer for '%s', name);
return -1;
@@ -58,22 +59,57 @@ static int freeze_unfreeze(const char *name, int freeze)
 
if (freeze) {
f = FROZEN;
-   ret = write(fd, f, strlen(f) + 1)  0;
+   ret = write(fd, f, strlen(f) + 1);
} else {
f = THAWED;
-   ret = write(fd, f, strlen(f) + 1)  0;
+   ret = write(fd, f, strlen(f) + 1);
 
/* compatibility code with old freezer interface */
-   if (ret) {
+   if (ret  0) {
f = RUNNING;
ret = write(fd, f, strlen(f) + 1)  0;
}
}
 
-   close(fd);
-   if (ret) 
-   SYSERROR(failed to write to '%s', freezer);
+   if (ret  0) {
+   SYSERROR(failed to write '%s' to '%s', f, freezer);
+   goto out;
+   }
+
+   while (1) {
+   ret = lseek(fd, 0L, SEEK_SET);
+   if (ret  0) {
+   SYSERROR(failed to lseek on file '%s', freezer);
+   goto out;
+   }
+
+   ret = read(fd, tmpf, sizeof(tmpf));
+   if (ret  0) {
+   SYSERROR(failed to read to '%s', freezer);
+   goto out;
+   }
+
+   ret = strncmp(f, tmpf, strlen(f));
+   if (!ret)
+   break;  /* Success */
 
+   sleep(1);
+
+   ret = lseek(fd, 0L, SEEK_SET);
+   if (ret  0) {
+   SYSERROR(failed to lseek on file '%s', freezer);
+   goto out;
+   }
+
+   ret = write(fd, f, strlen(f) + 1); 
+   if (ret  0) {
+   SYSERROR(failed to write '%s' to '%s', f, freezer);
+   goto out;
+   }
+   }
+
+out:
+   close(fd);
return ret;
 }
 
-- 
1.6.0.4


--
This SF.net email is sponsored by Sprint
What will you do first with EVO, the first 4G phone?
Visit sprint.com/first -- http://p.sf.net/sfu/sprint-com-first
___
Lxc-devel mailing list
Lxc-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/lxc-devel