dmaengine: pl330: fix double lock

The static bug finder EBA (http://www.iagoabal.eu/eba/) reported the
following double-lock bug:

    Double lock:
    1. spin_lock_irqsave(pch->lock, flags) at pl330_free_chan_resources:2236;
    2. call to function `pl330_release_channel' immediately after;
    3. call to function `dma_pl330_rqcb' in line 1753;
    4. spin_lock_irqsave(pch->lock, flags) at dma_pl330_rqcb:1505.

I have fixed it as suggested by Marek Szyprowski.

First, I have replaced `pch->lock' with `pl330->lock' in functions
`pl330_alloc_chan_resources' and `pl330_free_chan_resources'. This avoids
the double-lock by acquiring a different lock than `dma_pl330_rqcb'.

NOTE that, as a result, `pl330_free_chan_resources' executes
`list_splice_tail_init' on `pch->work_list' under lock `pl330->lock',
whereas in the rest of the code `pch->work_list' is protected by
`pch->lock'. I don't know if this may cause race conditions. Similarly
`pch->cyclic' is written by `pl330_alloc_chan_resources' under
`pl330->lock' but read by `pl330_tx_submit' under `pch->lock'.

Second, I have removed locking from `pl330_request_channel' and
`pl330_release_channel' functions. Function `pl330_request_channel' is
only called from `pl330_alloc_chan_resources', so the lock is already
held. Function `pl330_release_channel' is called from
`pl330_free_chan_resources', which already holds the lock, and from
`pl330_del'. Function `pl330_del' is called in an error path of
`pl330_probe' and at the end of `pl330_remove', but I assume that there
cannot be concurrent accesses to the protected data at those points.

Signed-off-by: Iago Abal <mail@iagoabal.eu>
Reviewed-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

path: root/include/net/Space.h

/* A unified ethernet device probe.  This is the easiest way to have every
 * ethernet adaptor have the name "eth[0123...]".
 */

struct net_device *hp100_probe(int unit);
struct net_device *ultra_probe(int unit);
struct net_device *wd_probe(int unit);
struct net_device *ne_probe(int unit);
struct net_device *fmv18x_probe(int unit);
struct net_device *i82596_probe(int unit);
struct net_device *ni65_probe(int unit);
struct net_device *sonic_probe(int unit);
struct net_device *smc_init(int unit);
struct net_device *atarilance_probe(int unit);
struct net_device *sun3lance_probe(int unit);
struct net_device *sun3_82586_probe(int unit);
struct net_device *apne_probe(int unit);
struct net_device *cs89x0_probe(int unit);
struct net_device *mvme147lance_probe(int unit);
struct net_device *tc515_probe(int unit);
struct net_device *lance_probe(int unit);
struct net_device *mac8390_probe(int unit);
struct net_device *mac89x0_probe(int unit);
struct net_device *cops_probe(int unit);
struct net_device *ltpc_probe(void);

/* Fibre Channel adapters */
int iph5526_probe(struct net_device *dev);

/* SBNI adapters */
int sbni_probe(int unit);