* writing to sysfs appears to hang
@ 2002-11-15 23:00 Paul Larson
2002-11-16 0:47 ` Mike Anderson
0 siblings, 1 reply; 6+ messages in thread
From: Paul Larson @ 2002-11-15 23:00 UTC (permalink / raw)
To: lkml
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I've been playing with sysfs and notices something odd. If I do this:
echo 1 > /sys/devices/sys/name
the process appears to be hung. ^c won't return control to me. If I
log in on another console though, I can't find it running in the process
list. All I can do is kill the login process. No kernel errors when I
do this, just the hung terminal.
-Paul Larson
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: writing to sysfs appears to hang
2002-11-15 23:00 writing to sysfs appears to hang Paul Larson
@ 2002-11-16 0:47 ` Mike Anderson
2002-11-19 17:02 ` Jens Axboe
0 siblings, 1 reply; 6+ messages in thread
From: Mike Anderson @ 2002-11-16 0:47 UTC (permalink / raw)
To: Paul Larson; +Cc: lkml
Paul Larson [plars@linuxtestproject.org] wrote:
> I've been playing with sysfs and notices something odd. If I do this:
> echo 1 > /sys/devices/sys/name
> the process appears to be hung. ^c won't return control to me. If I
> log in on another console though, I can't find it running in the process
> list. All I can do is kill the login process. No kernel errors when I
> do this, just the hung terminal.
>
> -Paul Larson
I repeated your example and in a quick look at the backtrace
the echo is in a loop calling down into sysfs_write_file/dev_attr_store.
I think the problem is that if a device does not have a attribute store
function the return value from dev_attr_store is incorrect.
-andmike
--
Michael Anderson
andmike@us.ibm.com
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: writing to sysfs appears to hang
2002-11-16 0:47 ` Mike Anderson
@ 2002-11-19 17:02 ` Jens Axboe
2002-11-20 17:24 ` Paul Larson
0 siblings, 1 reply; 6+ messages in thread
From: Jens Axboe @ 2002-11-19 17:02 UTC (permalink / raw)
To: Paul Larson, lkml
On Fri, Nov 15 2002, Mike Anderson wrote:
> Paul Larson [plars@linuxtestproject.org] wrote:
> > I've been playing with sysfs and notices something odd. If I do this:
> > echo 1 > /sys/devices/sys/name
> > the process appears to be hung. ^c won't return control to me. If I
> > log in on another console though, I can't find it running in the process
> > list. All I can do is kill the login process. No kernel errors when I
> > do this, just the hung terminal.
> >
> > -Paul Larson
>
> I repeated your example and in a quick look at the backtrace
> the echo is in a loop calling down into sysfs_write_file/dev_attr_store.
>
> I think the problem is that if a device does not have a attribute store
> function the return value from dev_attr_store is incorrect.
This has been in the deadline-rbtree patches for some time (uses writes
to sysfs, too).
===== fs/sysfs/inode.c 1.59 vs edited =====
--- 1.59/fs/sysfs/inode.c Wed Oct 30 21:27:35 2002
+++ edited/fs/sysfs/inode.c Fri Nov 8 14:33:59 2002
@@ -243,7 +243,7 @@
if (kobj && kobj->subsys)
ops = kobj->subsys->sysfs_ops;
if (!ops || !ops->store)
- return 0;
+ return -EINVAL;
page = (char *)__get_free_page(GFP_KERNEL);
if (!page)
--
Jens Axboe
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: writing to sysfs appears to hang
2002-11-19 17:02 ` Jens Axboe
@ 2002-11-20 17:24 ` Paul Larson
2002-11-20 19:14 ` Jens Axboe
0 siblings, 1 reply; 6+ messages in thread
From: Paul Larson @ 2002-11-20 17:24 UTC (permalink / raw)
To: Jens Axboe; +Cc: lkml, davej
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On Tue, 2002-11-19 at 11:02, Jens Axboe wrote:
> This has been in the deadline-rbtree patches for some time (uses writes
> to sysfs, too).
>
> ===== fs/sysfs/inode.c 1.59 vs edited =====
> --- 1.59/fs/sysfs/inode.c Wed Oct 30 21:27:35 2002
> +++ edited/fs/sysfs/inode.c Fri Nov 8 14:33:59 2002
> @@ -243,7 +243,7 @@
> if (kobj && kobj->subsys)
> ops = kobj->subsys->sysfs_ops;
> if (!ops || !ops->store)
> - return 0;
> + return -EINVAL;
>
> page = (char *)__get_free_page(GFP_KERNEL);
> if (!page)
No effect, the behaviour is still the same for me.
-Paul Larson
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: writing to sysfs appears to hang
2002-11-20 17:24 ` Paul Larson
@ 2002-11-20 19:14 ` Jens Axboe
2002-11-20 19:33 ` Patrick Mochel
0 siblings, 1 reply; 6+ messages in thread
From: Jens Axboe @ 2002-11-20 19:14 UTC (permalink / raw)
To: Paul Larson; +Cc: lkml, davej, Patrick Mochel
On Wed, Nov 20 2002, Paul Larson wrote:
> On Tue, 2002-11-19 at 11:02, Jens Axboe wrote:
> > This has been in the deadline-rbtree patches for some time (uses writes
> > to sysfs, too).
> >
> > ===== fs/sysfs/inode.c 1.59 vs edited =====
> > --- 1.59/fs/sysfs/inode.c Wed Oct 30 21:27:35 2002
> > +++ edited/fs/sysfs/inode.c Fri Nov 8 14:33:59 2002
> > @@ -243,7 +243,7 @@
> > if (kobj && kobj->subsys)
> > ops = kobj->subsys->sysfs_ops;
> > if (!ops || !ops->store)
> > - return 0;
> > + return -EINVAL;
> >
> > page = (char *)__get_free_page(GFP_KERNEL);
> > if (!page)
>
> No effect, the behaviour is still the same for me.
strace the program then, what is happening? What I saw was a program
seeing write() return 0, assuming it didn't write anything, rewrite the
whole thing. Repeat.
I bet this wouldn't happen if just sysfs didn't allow write open of a
file that doesn't have any writeable bits. Smells like another sysfs
bug. Pat?
--
Jens Axboe
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: writing to sysfs appears to hang
2002-11-20 19:14 ` Jens Axboe
@ 2002-11-20 19:33 ` Patrick Mochel
0 siblings, 0 replies; 6+ messages in thread
From: Patrick Mochel @ 2002-11-20 19:33 UTC (permalink / raw)
To: Jens Axboe; +Cc: Paul Larson, lkml, davej
On Wed, 20 Nov 2002, Jens Axboe wrote:
> On Wed, Nov 20 2002, Paul Larson wrote:
> > On Tue, 2002-11-19 at 11:02, Jens Axboe wrote:
> > > This has been in the deadline-rbtree patches for some time (uses writes
> > > to sysfs, too).
> > >
> > > ===== fs/sysfs/inode.c 1.59 vs edited =====
> > > --- 1.59/fs/sysfs/inode.c Wed Oct 30 21:27:35 2002
> > > +++ edited/fs/sysfs/inode.c Fri Nov 8 14:33:59 2002
> > > @@ -243,7 +243,7 @@
> > > if (kobj && kobj->subsys)
> > > ops = kobj->subsys->sysfs_ops;
> > > if (!ops || !ops->store)
> > > - return 0;
> > > + return -EINVAL;
> > >
> > > page = (char *)__get_free_page(GFP_KERNEL);
> > > if (!page)
> >
> > No effect, the behaviour is still the same for me.
>
> strace the program then, what is happening? What I saw was a program
> seeing write() return 0, assuming it didn't write anything, rewrite the
> whole thing. Repeat.
>
> I bet this wouldn't happen if just sysfs didn't allow write open of a
> file that doesn't have any writeable bits. Smells like another sysfs
> bug. Pat?
Yes, it is. The attached patch (relative to current BK) should fix it. I'm
planning on sending Linus an update soon, and this is in it.
-pat
--- linux-2.5-virgin/fs/sysfs/inode.c Wed Nov 20 12:13:06 2002
+++ linux-2.5-kobject/fs/sysfs/inode.c Wed Nov 20 12:15:18 2002
@@ -23,6 +23,8 @@
* Please see Documentation/filesystems/sysfs.txt for more information.
*/
+#undef DEBUG
+
#include <linux/list.h>
#include <linux/init.h>
#include <linux/pagemap.h>
@@ -173,17 +175,11 @@
sysfs_read_file(struct file *file, char *buf, size_t count, loff_t *ppos)
{
struct attribute * attr = file->f_dentry->d_fsdata;
- struct sysfs_ops * ops = NULL;
- struct kobject * kobj;
+ struct sysfs_ops * ops = file->private_data;
+ struct kobject * kobj = file->f_dentry->d_parent->d_fsdata;
unsigned char *page;
ssize_t retval = 0;
- kobj = file->f_dentry->d_parent->d_fsdata;
- if (kobj && kobj->subsys)
- ops = kobj->subsys->sysfs_ops;
- if (!ops || !ops->show)
- return 0;
-
if (count > PAGE_SIZE)
count = PAGE_SIZE;
@@ -234,16 +230,11 @@
sysfs_write_file(struct file *file, const char *buf, size_t count, loff_t *ppos)
{
struct attribute * attr = file->f_dentry->d_fsdata;
- struct sysfs_ops * ops = NULL;
- struct kobject * kobj;
+ struct sysfs_ops * ops = file->private_data;
+ struct kobject * kobj = file->f_dentry->d_parent->d_fsdata;
ssize_t retval = 0;
char * page;
- kobj = file->f_dentry->d_parent->d_fsdata;
- if (kobj && kobj->subsys)
- ops = kobj->subsys->sysfs_ops;
- if (!ops || !ops->store)
- return -EINVAL;
page = (char *)__get_free_page(GFP_KERNEL);
if (!page)
@@ -275,21 +266,72 @@
return retval;
}
-static int sysfs_open_file(struct inode * inode, struct file * filp)
+static int check_perm(struct inode * inode, struct file * file)
{
- struct kobject * kobj;
+ struct kobject * kobj = kobject_get(file->f_dentry->d_parent->d_fsdata);
+ struct attribute * attr = file->f_dentry->d_fsdata;
+ struct sysfs_ops * ops = NULL;
int error = 0;
- kobj = filp->f_dentry->d_parent->d_fsdata;
- if ((kobj = kobject_get(kobj))) {
- struct attribute * attr = filp->f_dentry->d_fsdata;
- if (!attr)
- error = -EINVAL;
- } else
- error = -EINVAL;
+ if (!kobj || !attr)
+ goto Einval;
+
+ if (kobj->subsys)
+ ops = kobj->subsys->sysfs_ops;
+
+ /* No sysfs operations, either from having no subsystem,
+ * or the subsystem have no operations.
+ */
+ if (!ops)
+ goto Eaccess;
+
+ /* File needs write support.
+ * The inode's perms must say it's ok,
+ * and we must have a store method.
+ */
+ if (file->f_mode & FMODE_WRITE) {
+
+ if (!(inode->i_mode & S_IWUGO))
+ goto Eperm;
+ if (!ops->store)
+ goto Eaccess;
+
+ }
+
+ /* File needs read support.
+ * The inode's perms must say it's ok, and we there
+ * must be a show method for it.
+ */
+ if (file->f_mode & FMODE_READ) {
+ if (!(inode->i_mode & S_IRUGO))
+ goto Eperm;
+ if (!ops->show)
+ goto Eaccess;
+ }
+
+ /* No error? Great, store the ops in file->private_data
+ * for easy access in the read/write functions.
+ */
+ file->private_data = ops;
+ goto Done;
+
+ Einval:
+ error = -EINVAL;
+ goto Done;
+ Eaccess:
+ error = -EACCES;
+ goto Done;
+ Eperm:
+ error = -EPERM;
+ Done:
return error;
}
+static int sysfs_open_file(struct inode * inode, struct file * filp)
+{
+ return check_perm(inode,filp);
+}
+
static int sysfs_release(struct inode * inode, struct file * filp)
{
struct kobject * kobj = filp->f_dentry->d_parent->d_fsdata;
^ permalink raw reply [flat|nested] 6+ messages in thread
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Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
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2002-11-15 23:00 writing to sysfs appears to hang Paul Larson
2002-11-16 0:47 ` Mike Anderson
2002-11-19 17:02 ` Jens Axboe
2002-11-20 17:24 ` Paul Larson
2002-11-20 19:14 ` Jens Axboe
2002-11-20 19:33 ` Patrick Mochel
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