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staging: unisys: visorbus: visorchannel: Refactor locking code to be statically deterministic. 

This patch makes locking in visorchannel_signalempty statically
deterministic.
As a result this patch fixes the sparse warning:
Context imbalance in 'visorchannel_signalempty' - different lock
contexts for basic block.

The logic of the locking code doesn't change but the layout of the
original code is "frowned upon"
according to mails on sparse context checking.
Refactoring removes the warning and makes the code more readable.

Signed-off-by: Cathal Mullaney <chuckleberryfinn@gmail.com>
Tested-by: David Kershner <david.kershner@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Cathal Mullaney 2016-10-19 22:43:25 +01:00 committed by Greg Kroah-Hartman
parent e0e6964805
commit f0208b7155
1 changed files with 19 additions and 11 deletions
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30
drivers/staging/unisys/visorbus/visorchannel.c
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@ -300,22 +300,30 @@ EXPORT_SYMBOL_GPL(visorchannel_signalremove);
* Return: boolean indicating whether any messages in the designated
* channel/queue are present
*/
static bool
queue_empty(struct visorchannel *channel, u32 queue)
{
struct signal_queue_header sig_hdr;
if (sig_read_header(channel, queue, &sig_hdr))
return true;
return (sig_hdr.head == sig_hdr.tail);
}
bool
visorchannel_signalempty(struct visorchannel *channel, u32 queue)
{
unsigned long flags = 0;
struct signal_queue_header sig_hdr;
bool rc = false;
bool rc;
unsigned long flags;
if (channel->needs_lock)
spin_lock_irqsave(&channel->remove_lock, flags);
if (!channel->needs_lock)
return queue_empty(channel, queue);
if (sig_read_header(channel, queue, &sig_hdr))
rc = true;
if (sig_hdr.head == sig_hdr.tail)
rc = true;
if (channel->needs_lock)
spin_unlock_irqrestore(&channel->remove_lock, flags);
spin_lock_irqsave(&channel->remove_lock, flags);
rc = queue_empty(channel, queue);
spin_unlock_irqrestore(&channel->remove_lock, flags);
return rc;
}