diff options
| author | Peter Hurley <peter@hurleysoftware.com> | 2013-06-15 15:14:30 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-07-24 01:43:02 +0200 |
| commit | fb7aa03db605e4f0b9a62cd4c77177c2596edd95 (patch) | |
| tree | 503946923a498b938aa849457310ceedaefbd806 | |
| parent | n_tty: Don't wait for buffer work in read() loop (diff) | |
| download | linux-fb7aa03db605e4f0b9a62cd4c77177c2596edd95.tar.xz linux-fb7aa03db605e4f0b9a62cd4c77177c2596edd95.zip | |
n_tty: Separate buffer indices to prevent cache-line sharing
If the read buffer indices are in the same cache-line, cpus will
contended over the cache-line (so called 'false sharing').
Separate the producer-published fields from the consumer-published
fields; document the locks relevant to each field.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/tty/n_tty.c | 21 |
1 files changed, 15 insertions, 6 deletions
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index a6eea30d0911..d0c8805d8131 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -82,29 +82,38 @@ #endif struct n_tty_data { - unsigned int column; + /* producer-published */ + size_t read_head; + size_t canon_head; + DECLARE_BITMAP(process_char_map, 256); + + /* private to n_tty_receive_overrun (single-threaded) */ unsigned long overrun_time; int num_overrun; /* non-atomic */ bool no_room; + /* must hold exclusive termios_rwsem to reset these */ unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1; unsigned char echo_overrun:1; - DECLARE_BITMAP(process_char_map, 256); + /* shared by producer and consumer */ + char *read_buf; DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE); - char *read_buf; - size_t read_head; - size_t read_tail; int minimum_to_wake; + /* consumer-published */ + size_t read_tail; + + /* protected by echo_lock */ unsigned char *echo_buf; unsigned int echo_pos; unsigned int echo_cnt; - size_t canon_head; + /* protected by output lock */ + unsigned int column; unsigned int canon_column; struct mutex atomic_read_lock; |