Module: xenomai-jki
Branch: queues/proc
Commit: 910b33ec9954e051ae16066b5e17d3a888764b89
URL:
http://git.xenomai.org/?p=xenomai-jki.git;a=commit;h=910b33ec9954e051ae16066b5e17d3a888764b89
Author: Jan Kiszka <jan.kis...@siemens.com>
Date: Thu Apr 1 15:10:19 2010 +0200
RTDM: Plug race between proc_read_dev_info and device deregistration
As the device references passed to proc_read_dev_info may become invalid
while we dereference it, we need to acquire nrt_dev_lock and check the
pointer against our list of registered devices.
Signed-off-by: Jan Kiszka <jan.kis...@siemens.com>
---
ksrc/skins/rtdm/proc.c | 29 ++++++++++++++++++++++++++---
1 files changed, 26 insertions(+), 3 deletions(-)
diff --git a/ksrc/skins/rtdm/proc.c b/ksrc/skins/rtdm/proc.c
index c797764..b889f73 100644
--- a/ksrc/skins/rtdm/proc.c
+++ b/ksrc/skins/rtdm/proc.c
@@ -203,11 +203,33 @@ static int proc_read_fildes(char *buf, char **start,
off_t offset,
static int proc_read_dev_info(char *buf, char **start, off_t offset,
int count, int *eof, void *data)
{
- /* accessing the device during unregister (remove_proc_entry) might be
- racy, but no official workaround is known yet */
- struct rtdm_device *device = data;
+ struct rtdm_device *device;
+ int i;
RTDM_PROC_PRINT_VARS(256);
+ if (down_interruptible(&nrt_dev_lock))
+ return -ERESTARTSYS;
+
+ /*
+ * As the device may have disappeared while the handler was called,
+ * first match the pointer against registered devices.
+ */
+ for (i = 0; i < devname_hashtab_size; i++)
+ list_for_each_entry(device, &rtdm_named_devices[i],
+ reserved.entry)
+ if (device == data)
+ goto found;
+
+ for (i = 0; i < protocol_hashtab_size; i++)
+ list_for_each_entry(device, &rtdm_protocol_devices[i],
+ reserved.entry)
+ if (device == data)
+ goto found;
+
+ up(&nrt_dev_lock);
+ return -ENODEV;
+
+found:
if (!RTDM_PROC_PRINT("driver:\t\t%s\nversion:\t%d.%d.%d\n",
device->driver_name,
RTDM_DRIVER_MAJOR_VER(device->driver_version),
@@ -232,6 +254,7 @@ static int proc_read_dev_info(char *buf, char **start,
off_t offset,
atomic_read(&device->reserved.refcount));
done:
+ up(&nrt_dev_lock);
RTDM_PROC_PRINT_DONE;
}
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