Re: [PATCH v9 14/17] tpm: remove TPM_TRANSMIT_UNLOCKED flag

[Jason Gunthorpe <jgg@ziepe.ca>]

On Sun, Nov 18, 2018 at 02:47:47PM +0200, Jarkko Sakkinen wrote:
> Added locking as part of tpm_try_get_ops() and tpm_put_ops() as they are
> anyway used in most of the call sites except in tpmrm_release() where we
> take the locks manually.
> 
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
> ---
>  drivers/char/tpm/tpm-chip.c       |  2 ++
>  drivers/char/tpm/tpm-dev-common.c |  4 +---
>  drivers/char/tpm/tpm-interface.c  |  8 --------
>  drivers/char/tpm/tpm.h            |  8 ++------
>  drivers/char/tpm/tpm2-cmd.c       | 13 ++++---------
>  drivers/char/tpm/tpm2-space.c     | 15 ++++++---------
>  6 files changed, 15 insertions(+), 35 deletions(-)
 
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index 32db84683c40..157505b0f755 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -58,6 +58,7 @@ int tpm_try_get_ops(struct tpm_chip *chip)
>  	if (!chip->ops)
>  		goto out_lock;
>  
> +	mutex_lock(&chip->tpm_mutex);
>  	return 0;

It really isn't appropriate for something called 'get' to be exclusive
like this.. Call it tpm_try_lock_ops() ?

> diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
> index c7dc54930576..582caefcf19b 100644
> --- a/drivers/char/tpm/tpm-dev-common.c
> +++ b/drivers/char/tpm/tpm-dev-common.c
> @@ -33,7 +33,6 @@ static ssize_t tpm_dev_transmit(struct tpm_chip *chip, struct tpm_space *space,
>  	struct tpm_header *header = (void *)buf;
>  	ssize_t ret, len;
>  
> -	mutex_lock(&chip->tpm_mutex);

The now implicit locking should be tested for using lockdep calls in
all places that assume the lock is held by the caller.

Jason