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    • Alan Stern's avatar
      USB: f_mass_storage: improve memory barriers and synchronization · 225785ae
      Alan Stern authored 
      

This patch reworks the way f_mass_storage.c handles memory barriers
and synchronization:

	The driver now uses a wait_queue instead of doing its own
	task-state manipulations (even though only one task will ever
	use the wait_queue).

	The thread_wakeup_needed variable is removed.  It was only a
	source of trouble; although it was what the driver tested to
	see whether it should wake up, what we really wanted to see
	was whether a USB transfer had completed.

	All the explicit memory barriers scattered throughout the
	driver are replaced by a few calls to smp_load_acquire() and
	smp_store_release().

	The inreq_busy and outreq_busy fields are removed.  In their
	place, the driver keeps track of the current I/O direction by
	splitting BUF_STATE_BUSY into two states: BUF_STATE_SENDING
	and BUF_STATE_RECEIVING.

	The buffer states are no longer protected by a lock.  Mutual
	exclusion isn't needed; the state is changed only by the
	driver's main thread when it owns the buffer, and only by the
	request completion routine when the gadget core owns the buffer.

	The do_write() and throw_away_data() routines were reorganized
	to make efficient use of the new sleeping mechanism.  This
	resulted in the removal of one indentation level in those
	routines, making the patch appear to be more more complicated
	than it really is.

	In a few places, the driver allowed itself to be frozen although
	it really shouldn't have (in the middle of executing a SCSI
	command).  Those places have been fixed.

	The logic in the exception handler for aborting transfers and
	waiting for them to stop has been simplified.

Tested-by: default avatarThinh Nguyen <thinhn@synopsys.com>
Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarFelipe Balbi <felipe.balbi@linux.intel.com>
      225785ae
    • Alan Stern's avatar
      USB: f_mass_storage: improve async notification handling · 78db441d
      Alan Stern authored 
      

This patch makes several adjustments to the way f_mass_storage.c
handles its internal state and asynchronous notifications (AKA
exceptions):

	A number of states weren't being used for anything.
	They are removed.

	The FSG_STATE_IDLE state was renamed to FSG_STATE_NORMAL,
	because it now applies whenever the gadget is operating
	normally, not just when the gadget is idle.

	The FSG_STATE_RESET state was renamed to
	FSG_STATE_PROTOCOL_RESET, indicating that it represents a
	Bulk-Only Transport protocol reset and not a general USB
	reset.

	When a signal arrives, it's silly for the signal handler to
	send itself another signal!  Now it takes care of everything
	inline.

Along with an assortment of other minor changes in the same category.

Tested-by: default avatarThinh Nguyen <thinhn@synopsys.com>
Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarFelipe Balbi <felipe.balbi@linux.intel.com>
      78db441d