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    SubjectRe: [PATCH AUTOSEL 5.5 542/542] pipe: use exclusive waits when reading or writing
    On Tue, Feb 18, 2020 at 10:20 AM Matthew Wilcox <willy@infradead.org> wrote:
    >
    > You don't want to move wake_up_partner() up and call it from pipe_release()?

    I was actually thinking of going the other way - two of three users of
    wake_up_partner() are redundantly waking up the wrong side, and the
    third user is pointlessly written too.

    So I was _thinking_ of a patch like the appended (which is on top of
    the previous patch), but ended up not doing it. Until you brought it
    up.

    But I won't bother committing this, since it shouldn't really matter.

    Linus
    fs/pipe.c | 18 ++++++------------
    1 file changed, 6 insertions(+), 12 deletions(-)

    diff --git a/fs/pipe.c b/fs/pipe.c
    index 2144507447c5..79ba61430f9c 100644
    --- a/fs/pipe.c
    +++ b/fs/pipe.c
    @@ -1025,12 +1025,6 @@ static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
    return cur == *cnt ? -ERESTARTSYS : 0;
    }

    -static void wake_up_partner(struct pipe_inode_info *pipe)
    -{
    - wake_up_interruptible_all(&pipe->rd_wait);
    - wake_up_interruptible_all(&pipe->wr_wait);
    -}
    -
    static int fifo_open(struct inode *inode, struct file *filp)
    {
    struct pipe_inode_info *pipe;
    @@ -1078,7 +1072,7 @@ static int fifo_open(struct inode *inode, struct file *filp)
    */
    pipe->r_counter++;
    if (pipe->readers++ == 0)
    - wake_up_partner(pipe);
    + wake_up_interruptible_all(&pipe->wr_wait);

    if (!is_pipe && !pipe->writers) {
    if ((filp->f_flags & O_NONBLOCK)) {
    @@ -1104,7 +1098,7 @@ static int fifo_open(struct inode *inode, struct file *filp)

    pipe->w_counter++;
    if (!pipe->writers++)
    - wake_up_partner(pipe);
    + wake_up_interruptible_all(&pipe->rd_wait);

    if (!is_pipe && !pipe->readers) {
    if (wait_for_partner(pipe, &pipe->r_counter))
    @@ -1120,12 +1114,12 @@ static int fifo_open(struct inode *inode, struct file *filp)
    * the process can at least talk to itself.
    */

    - pipe->readers++;
    - pipe->writers++;
    + if (pipe->readers++ == 0)
    + wake_up_interruptible_all(&pipe->wr_wait);
    + if (pipe->writers++ == 0)
    + wake_up_interruptible_all(&pipe->rd_wait);
    pipe->r_counter++;
    pipe->w_counter++;
    - if (pipe->readers == 1 || pipe->writers == 1)
    - wake_up_partner(pipe);
    break;

    default:
    \
     
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      Last update: 2020-02-18 19:29    [W:3.065 / U:0.040 seconds]
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