linux/drivers/tty/tty_buffer.c, branch v3.12.14

tty: Remove private constant from global namespace

2013-07-23T23:47:10Z

TTY_BUFFER_PAGE is only used within drivers/tty/tty_buffer.c; relocate to that file scope. Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman

tty: Fix unsafe vt paste_selection()

2013-07-23T23:47:10Z

Convert the tty_buffer_flush() exclusion mechanism to a public interface - tty_buffer_lock/unlock_exclusive() - and use the interface to safely write the paste selection to the line discipline. Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman

tty: Merge __tty_flush_buffer() into lone call site

2013-07-23T23:47:09Z

__tty_flush_buffer() is now only called by tty_flush_buffer(); merge functions. Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman

tty: Use non-atomic state to signal flip buffer flush pending

2013-07-23T23:47:09Z

Atomic bit ops are no longer required to indicate a flip buffer flush is pending, as the flush_mutex is sufficient barrier. Remove the unnecessary port .iflags field and localize flip buffer state to struct tty_bufhead. Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman

tty: Only perform flip buffer flush from tty_buffer_flush()

2013-07-23T23:47:09Z

Now that dropping the buffer lock is not necessary (as result of converting the spin lock to a mutex), the flip buffer flush no longer needs to be handled by the buffer work. Simply signal a flush is required; the buffer work will exit the i/o loop, which allows tty_buffer_flush() to proceed. Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman

tty: Ensure single-threaded flip buffer consumer with mutex

2013-07-23T23:47:09Z

The buffer work may race with parallel tty_buffer_flush. Use a mutex to guarantee exclusive modify access to the head flip buffer. Remove the unneeded spin lock. Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman

tty: Make driver-side flip buffers lockless

2013-07-23T23:47:09Z

Driver-side flip buffer input is already single-threaded; 'publish' the .next link as the last operation on the tail buffer so the 'consumer' sees the already-completed flip buffer. The commit buffer index is already 'published' by driver-side functions. Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman

tty: Track flip buffer memory limit atomically

2013-07-23T23:47:08Z

Lockless flip buffers require atomically updating the bytes-in-use watermark. The pty driver also peeks at the watermark value to limit memory consumption to a much lower value than the default; query the watermark with new fn, tty_buffer_space_avail(). Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman

tty: Simplify flip buffer list with 0-sized sentinel

2013-07-23T23:47:08Z

Use a 0-sized sentinel to avoid assigning the head ptr from the driver side thread. This also eliminates testing head/tail for NULL. When the sentinel is first 'consumed' by the buffer work (or by tty_buffer_flush()), it is detached from the list but not freed nor added to the free list. Both buffer work and tty_buffer_flush() continue to preserve at least 1 flip buffer to which head & tail is pointed. Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman

tty: Use lockless flip buffer free list

2013-07-23T23:47:08Z

In preparation for lockless flip buffers, make the flip buffer free list lockless. NB: using llist is not the optimal solution, as the driver and buffer work may contend over the llist head unnecessarily. However, test measurements indicate this contention is low. Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman