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gpu: nvgpu: hold ch ref when getting ch from fd

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Fix a race condition in gk20a_get_channel_from_file() that returns a
channel pointer from an fd: take a reference to the channel before
putting the file ref back. Now the caller is responsible of releasing
the channel reference eventually.

Also document why dbg_session_channel_data has to hold a ref to the
channel file instead of just the channel: that might deadlock if the fds
were closed in "wrong" order.

Change-Id: I8e91b809f5f7b1cb0c1487bd955ad6d643727a53
Signed-off-by: Konsta Holtta <kholtta@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1549290
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>
This commit is contained in:
Konsta Holtta
2017-08-31 13:01:26 +03:00
committed by mobile promotions
parent de0ce3e017
commit 17451138cf
6 changed files with 58 additions and 16 deletions
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10
drivers/gpu/nvgpu/common/linux/ioctl_channel.c
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@@ -260,8 +260,15 @@ static int gk20a_init_error_notifier(struct channel_gk20a *ch,
return 0;
}
/*
* This returns the channel with a reference. The caller must
* gk20a_channel_put() the ref back after use.
*
* NULL is returned if the channel was not found.
*/
struct channel_gk20a *gk20a_get_channel_from_file(int fd)
{
struct channel_gk20a *ch;
struct channel_priv *priv;
struct file *f = fget(fd);
@@ -274,8 +281,9 @@ struct channel_gk20a *gk20a_get_channel_from_file(int fd)
}
priv = (struct channel_priv *)f->private_data;
ch = gk20a_channel_get(priv->c);
fput(f);
return priv->c;
return ch;
}
int gk20a_channel_release(struct inode *inode, struct file *filp)