On Wed, Nov 25, 2020 at 10:01 PM Stanimir Varbanov
<stanimir.varbanov@xxxxxxxxxx> wrote:
>
>
>
> On 11/25/20 5:46 AM, Alexandre Courbot wrote:
> > On Fri, Nov 20, 2020 at 9:12 AM Stanimir Varbanov
> > <stanimir.varbanov@xxxxxxxxxx> wrote:
> >>
> >> Currently we rely on firmware to return error when we reach the maximum
> >> supported number of sessions. But this errors are happened at reqbuf
> >> time which is a bit later. The more reasonable way looks like is to
> >> return the error on driver open.
> >>
> >> To achieve that modify hfi_session_create to return error when we reach
> >> maximum count of sessions and thus refuse open.
> >>
> >> Signed-off-by: Stanimir Varbanov <stanimir.varbanov@xxxxxxxxxx>
> >> ---
> >> drivers/media/platform/qcom/venus/core.h | 1 +
> >> drivers/media/platform/qcom/venus/hfi.c | 19 +++++++++++++++----
> >> .../media/platform/qcom/venus/hfi_parser.c | 3 +++
> >> 3 files changed, 19 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/drivers/media/platform/qcom/venus/core.h b/drivers/media/platform/qcom/venus/core.h
> >> index db0e6738281e..3a477fcdd3a8 100644
> >> --- a/drivers/media/platform/qcom/venus/core.h
> >> +++ b/drivers/media/platform/qcom/venus/core.h
> >> @@ -96,6 +96,7 @@ struct venus_format {
> >> #define MAX_CAP_ENTRIES 32
> >> #define MAX_ALLOC_MODE_ENTRIES 16
> >> #define MAX_CODEC_NUM 32
> >> +#define MAX_SESSIONS 16
> >>
> >> struct raw_formats {
> >> u32 buftype;
> >> diff --git a/drivers/media/platform/qcom/venus/hfi.c b/drivers/media/platform/qcom/venus/hfi.c
> >> index 638ed5cfe05e..8420be6d3991 100644
> >> --- a/drivers/media/platform/qcom/venus/hfi.c
> >> +++ b/drivers/media/platform/qcom/venus/hfi.c
> >> @@ -175,6 +175,7 @@ static int wait_session_msg(struct venus_inst *inst)
> >> int hfi_session_create(struct venus_inst *inst, const struct hfi_inst_ops *ops)
> >> {
> >> struct venus_core *core = inst->core;
> >> + int ret;
> >>
> >> if (!ops)
> >> return -EINVAL;
> >> @@ -183,12 +184,22 @@ int hfi_session_create(struct venus_inst *inst, const struct hfi_inst_ops *ops)
> >> init_completion(&inst->done);
> >> inst->ops = ops;
> >>
> >> - mutex_lock(&core->lock);
> >> - list_add_tail(&inst->list, &core->instances);
> >> - atomic_inc(&core->insts_count);
> >> + ret = mutex_lock_interruptible(&core->lock);
> >> + if (ret)
> >> + return ret;
> >
> > Why do we change to mutex_lock_interruptible() here? This makes this
>
> Because mutex_lock_interruptible is preferable in kernel docs, but I
> agree that changing mutex_lock with mutex_lock_interruptible should be
> subject of another lock related patches. I will drop this in next patch
> version.
>
> > function return an error even though we could obtain the lock just by
> > trying a bit harder.
>
> I didn't get that. The behavior of mutex_lock_interruptible is that same
> as mutex_lock, i.e. the it will sleep to acquire the lock. The
> difference is that the sleep could be interrupted by a signal. You might
> think about mutex_trylock?
Unless that mutex can be held by someone else for a rather long time
(i.e. to the point where we may want to give priority to signals when
userspace opens the device, since that's where hfi_session_create() is
called), I am not convinced this change is necessary? It may confuse
userspace into thinking there was a serious error while there is none.
Granted, userspace should manage this case, and from what I can see
this code is correct, but I'm not sure we would gain anything by
adding this extra complexity.
>
> >
> >> +
> >> + ret = atomic_read(&core->insts_count);
> >> + if (ret + 1 > core->max_sessions_supported) {
> >> + ret = -EAGAIN;
> >> + } else {
> >> + atomic_inc(&core->insts_count);
> >> + list_add_tail(&inst->list, &core->instances);
> >> + ret = 0;
> >> + }
> >> +
> >> mutex_unlock(&core->lock);
> >>
> >> - return 0;
> >> + return ret;
> >> }
> >> EXPORT_SYMBOL_GPL(hfi_session_create);
> >>
> >> diff --git a/drivers/media/platform/qcom/venus/hfi_parser.c b/drivers/media/platform/qcom/venus/hfi_parser.c
> >> index 363ee2a65453..52898633a8e6 100644
> >> --- a/drivers/media/platform/qcom/venus/hfi_parser.c
> >> +++ b/drivers/media/platform/qcom/venus/hfi_parser.c
> >> @@ -276,6 +276,9 @@ u32 hfi_parser(struct venus_core *core, struct venus_inst *inst, void *buf,
> >> words_count--;
> >> }
> >>
> >> + if (!core->max_sessions_supported)
> >> + core->max_sessions_supported = MAX_SESSIONS;
> >> +
> >> parser_fini(inst, codecs, domain);
> >>
> >> return HFI_ERR_NONE;
> >> --
> >> 2.17.1
> >>
>
> --
> regards,
> Stan
