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[media] soc-camera: properly fix camera probing races 

The recently introduced host_lock causes lockdep warnings, besides, list
enumeration in scan_add_host() must be protected by holdint the list_lock.
OTOH, holding .video_lock in soc_camera_open() isn't enough to protect
the host during its building of the pipeline, because .video_lock is per
soc-camera device. If, e.g. more than one sensor can be attached to a host
and the user tries to open both device nodes simultaneously, host's .add()
method can be called simultaneously for both sensors. Fix these problems
by holding list_lock instead of .host_lock in scan_add_host() and taking
it shortly at the beginning of soc_camera_open(), and using .host_lock to
protect host's .add() and .remove() operations only.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Guennadi Liakhovetski 2012-12-20 13:02:51 -03:00 committed by Mauro Carvalho Chehab
parent daf16bab1e
commit 7d051b35d5
2 changed files with 20 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
drivers/media/platform/soc_camera/soc_camera.c
View File

@ -517,7 +517,14 @@ static int soc_camera_open(struct file *file)
/* No device driver attached */
return -ENODEV;
/*
* Don't mess with the host during probe: wait until the loop in
* scan_add_host() completes
*/
if (mutex_lock_interruptible(&list_lock))
return -ERESTARTSYS;
ici = to_soc_camera_host(icd->parent);
mutex_unlock(&list_lock);
if (mutex_lock_interruptible(&icd->video_lock))
return -ERESTARTSYS;
@ -548,7 +555,6 @@ static int soc_camera_open(struct file *file)
if (icl->reset)
icl->reset(icd->pdev);
/* Don't mess with the host during probe */
mutex_lock(&ici->host_lock);
ret = ici->ops->add(icd);
mutex_unlock(&ici->host_lock);
@ -602,7 +608,9 @@ esfmt:
eresume:
__soc_camera_power_off(icd);
epower:
mutex_lock(&ici->host_lock);
ici->ops->remove(icd);
mutex_unlock(&ici->host_lock);
eiciadd:
icd->use_count--;
module_put(ici->ops->owner);
@ -625,7 +633,9 @@ static int soc_camera_close(struct file *file)
if (ici->ops->init_videobuf2)
vb2_queue_release(&icd->vb2_vidq);
mutex_lock(&ici->host_lock);
ici->ops->remove(icd);
mutex_unlock(&ici->host_lock);
__soc_camera_power_off(icd);
}
@ -1052,7 +1062,7 @@ static void scan_add_host(struct soc_camera_host *ici)
{
struct soc_camera_device *icd;
mutex_lock(&ici->host_lock);
mutex_lock(&list_lock);
list_for_each_entry(icd, &devices, list) {
if (icd->iface == ici->nr) {
@ -1061,7 +1071,7 @@ static void scan_add_host(struct soc_camera_host *ici)
}
}
mutex_unlock(&ici->host_lock);
mutex_unlock(&list_lock);
}
#ifdef CONFIG_I2C_BOARDINFO
@ -1148,7 +1158,9 @@ static int soc_camera_probe(struct soc_camera_device *icd)
if (icl->reset)
icl->reset(icd->pdev);
mutex_lock(&ici->host_lock);
ret = ici->ops->add(icd);
mutex_unlock(&ici->host_lock);
if (ret < 0)
goto eadd;
@ -1220,7 +1232,9 @@ static int soc_camera_probe(struct soc_camera_device *icd)
icd->field = mf.field;
}
mutex_lock(&ici->host_lock);
ici->ops->remove(icd);
mutex_unlock(&ici->host_lock);
mutex_unlock(&icd->video_lock);
@ -1242,7 +1256,9 @@ eadddev:
video_device_release(icd->vdev);
icd->vdev = NULL;
evdc:
mutex_lock(&ici->host_lock);
ici->ops->remove(icd);
mutex_unlock(&ici->host_lock);
eadd:
ereg:
v4l2_ctrl_handler_free(&icd->ctrl_handler);

2
include/media/soc_camera.h
View File

@ -62,7 +62,7 @@ struct soc_camera_device {
struct soc_camera_host {
struct v4l2_device v4l2_dev;
struct list_head list;
struct mutex host_lock; /* Protect during probing */
struct mutex host_lock; /* Protect pipeline modifications */
unsigned char nr; /* Host number */
u32 capabilities;
void *priv;