On Wed, 2011-01-19 at 16:10 +0300, Vasiliy Kulikov wrote:
> Hi,
>
> I've noticed that locking in drivers/media/dvb/frontends/dib9000.c is
> not correct:
>
> static int dib9000_fw_get_channel(...)
> {
> ...
> DibAcquireLock(&state->platform.risc.mem_mbx_lock);
> ...
>
> error:
> DibReleaseLock(&state->platform.risc.mem_mbx_lock);
> return ret;
> }
>
> #define DibAcquireLock(lock) do { if (mutex_lock_interruptible(lock) < 0)
> dprintk("could not get the lock"); } while (0)
> #define DibReleaseLock(lock) mutex_unlock(lock)
>
>
> 1) If mutex is not hold, then the critical section is not protected.
>
> 2) If mutex was not hold, then the code tries to release not holded
> mutex.
I didn't think that was a problem, because most callers didn't have code
to handle the error. and would therefore hopefully just call again.
What I noticed in particular the lock is never released on error
condition as in...
static int dib9000_read_ber(struct dvb_frontend *fe, u32 * ber)
{
struct dib9000_state *state = fe->demodulator_priv;
u16 c[16];
DibAcquireLock(&state->platform.risc.mem_mbx_lock);
if (dib9000_fw_memmbx_sync(state, FE_SYNC_CHANNEL) < 0)
return -EIO; <----------the lock is never
released.
dib9000_risc_mem_read(state, FE_MM_R_FE_MONITOR, (u8 *) c, sizeof(c));
DibReleaseLock(&state->platform.risc.mem_mbx_lock);
*ber = c[10] << 16 | c[11];
return 0;
}
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