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Date: Fri, 28 Sep 2012 10:52:50 +1000
From: Ryan Mallon <rmallon@...il.com>
To: Dave Jones <davej@...hat.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
"Myklebust, Trond" <Trond.Myklebust@...app.com>,
Joerg Roedel <joro@...tes.org>,
Joerg Roedel <joerg.roedel@....com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: BUG_ON/panic proliferation.
On 28/09/12 03:30, Dave Jones wrote:
> On Thu, Sep 27, 2012 at 09:59:13AM -0700, Linus Torvalds wrote:
>
> > We have too many f*cking BUG_ON's in the kernel, and the fact that one
> > triggers and it has taken a month and a half without it even being
> > resolved is a problem.
>
> This has bothered me for a while.
>
> $ rgrep BUG_ON drivers/ | wc -l
> 4018
> $ rgrep WARN_ON drivers/ | wc -l
> 2415
> $ rgrep panic drivers/ | wc -l
> 997
>
> $ rgrep BUG_ON fs | wc -l
> 2792
> $ rgrep WARN_ON fs | wc -l
> 524
> $ rgrep panic fs | wc -l
> 381
The situation isn't quite that bad. Your grep picks up a few variables
with panic in the name and some wrapper functions around panic. This
gets closer to the real counts (still finds some instances in comments):
$git grep "[^_]panic *(" drivers/ | wc -l
282
$git grep "[^_]panic *(" fs/ | wc -l
53
Some of those look reasonably easy to remove. For example, the panics in
the module_init path for drivers/tty/pty.c could be modified to simply
return -ENOMEM. Something like the below removes 9 panic calls
(completely untested).
~Ryan
---
Remove panic calls from drivers/tty/pty.c
There is no need to panic the system if the allocation/registration of
the pty drivers fails. Instead return an error and fail the module load.
Signed-off-by: Ryan Mallon <rmallon@...il.com>
diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index 5505ffc..69af453 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -382,20 +382,21 @@ static const struct tty_operations slave_pty_ops_bsd = {
.resize = pty_resize
};
-static void __init legacy_pty_init(void)
+static int __init legacy_pty_init(void)
{
struct tty_driver *pty_driver, *pty_slave_driver;
+ int err = -ENOMEM;
if (legacy_count <= 0)
- return;
+ return 0;
pty_driver = alloc_tty_driver(legacy_count);
if (!pty_driver)
- panic("Couldn't allocate pty driver");
+ goto fail;
pty_slave_driver = alloc_tty_driver(legacy_count);
if (!pty_slave_driver)
- panic("Couldn't allocate pty slave driver");
+ goto fail_put_pty_driver;
pty_driver->driver_name = "pty_master";
pty_driver->name = "pty";
@@ -429,13 +430,35 @@ static void __init legacy_pty_init(void)
pty_slave_driver->other = pty_driver;
tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
- if (tty_register_driver(pty_driver))
- panic("Couldn't register pty driver");
- if (tty_register_driver(pty_slave_driver))
- panic("Couldn't register pty slave driver");
+ err = tty_register_driver(pty_driver);
+ if (err)
+ goto fail_put_pty_slave_driver;
+ err = tty_register_driver(pty_slave_driver);
+ if (err)
+ goto fail_unregister_pty_driver;
+
+ return 0;
+
+fail_unregister_pty_driver:
+ tty_unregister_driver(pty_driver);
+fail_put_pty_slave_driver:
+ tty_driver_put(pty_slave_driver);
+fail_put_pty_driver:
+ tty_driver_put(pty_driver);
+fail:
+ return err;
+}
+
+static void __init legacy_pty_free(void)
+{
+ tty_unregister_driver(pty_slave_driver);
+ tty_unregister_driver(pty_driver);
+ tty_driver_put(pty_slave_driver);
+ tty_driver_put(pty_driver);
}
#else
static inline void legacy_pty_init(void) { }
+static inline void legacy_pty_free(void) { }
#endif
/* Unix98 devices */
@@ -670,14 +693,16 @@ err_file:
static struct file_operations ptmx_fops;
-static void __init unix98_pty_init(void)
+static int __init unix98_pty_init(void)
{
+ int err = -ENOMEM;
+
ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
if (!ptm_driver)
- panic("Couldn't allocate Unix98 ptm driver");
+ goto fail;
pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
if (!pts_driver)
- panic("Couldn't allocate Unix98 pts driver");
+ goto fail_put_ptm_driver;
ptm_driver->driver_name = "pty_master";
ptm_driver->name = "ptm";
@@ -712,20 +737,40 @@ static void __init unix98_pty_init(void)
pts_driver->other = ptm_driver;
tty_set_operations(pts_driver, &pty_unix98_ops);
- if (tty_register_driver(ptm_driver))
- panic("Couldn't register Unix98 ptm driver");
- if (tty_register_driver(pts_driver))
- panic("Couldn't register Unix98 pts driver");
+ err = tty_register_driver(ptm_driver);
+ if (err)
+ goto fail_put_pts_driver;
+ err = tty_register_driver(pts_driver);
+ if (err)
+ goto fail_unregister_ptm_driver;
/* Now create the /dev/ptmx special device */
tty_default_fops(&ptmx_fops);
ptmx_fops.open = ptmx_open;
cdev_init(&ptmx_cdev, &ptmx_fops);
- if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
- register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
- panic("Couldn't register /dev/ptmx driver\n");
+ err = cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1);
+ if (err)
+ goto fail_unregister_pts_driver;
+ err = register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx");
+ if (err)
+ goto fail_cdev_del;
+
device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
+ return 0;
+
+fail_cdev_del:
+ cdev_del(&ptmx_cdev);
+fail_unregister_pts_driver:
+ tty_unregister_driver(pts_driver);
+fail_unregister_ptm_driver:
+ tty_unregister_driver(ptm_driver);
+fail_put_pts_driver:
+ tty_put_driver(pts_driver);
+fail_put_ptm_driver:
+ tty_put_driver(ptm_driver);
+fail:
+ return err;
}
#else
@@ -734,8 +779,17 @@ static inline void unix98_pty_init(void) { }
static int __init pty_init(void)
{
- legacy_pty_init();
- unix98_pty_init();
+ int err;
+
+ err = legacy_pty_init();
+ if (err)
+ return err;
+
+ err = unix98_pty_init();
+ if (err) {
+ legacy_pty_free();
+ return err;
+ }
return 0;
}
module_init(pty_init);
--
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