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/uapi/asm-generic/mman.h

#ifndef __ASM_GENERIC_MMAN_H
#define __ASM_GENERIC_MMAN_H

#include <asm-generic/mman-common.h>

#define MAP_GROWSDOWN	0x0100		/* stack-like segment */
#define MAP_DENYWRITE	0x0800		/* ETXTBSY */
#define MAP_EXECUTABLE	0x1000		/* mark it as an executable */
#define MAP_LOCKED	0x2000		/* pages are locked */
#define MAP_NORESERVE	0x4000		/* don't check for reservations */
#define MAP_POPULATE	0x8000		/* populate (prefault) pagetables */
#define MAP_NONBLOCK	0x10000		/* do not block on IO */
#define MAP_STACK	0x20000		/* give out an address that is best suited for process/thread stacks */
#define MAP_HUGETLB	0x40000		/* create a huge page mapping */

/* Bits [26:31] are reserved, see mman-common.h for MAP_HUGETLB usage */

#define MCL_CURRENT	1		/* lock all current mappings */
#define MCL_FUTURE	2		/* lock all future mappings */
#define MCL_ONFAULT	4		/* lock all pages that are faulted in */

#endif /* __ASM_GENERIC_MMAN_H */