On 29.11.2012 17:54, Alan Cox wrote:
>> diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
>> index 6c9b7cd..4f02f9c 100644
>> --- a/drivers/tty/tty_buffer.c
>> +++ b/drivers/tty/tty_buffer.c
>> @@ -114,11 +114,14 @@ static void __tty_buffer_flush(struct tty_struct *tty)
>> {
>> struct tty_buffer *thead;
>>
>> - while ((thead = tty->buf.head) != NULL) {
>> - tty->buf.head = thead->next;
>> - tty_buffer_free(tty, thead);
>> + if (tty->buf.head == NULL)
>> + return;
>> + while ((thead = tty->buf.head->next) != NULL) {
>> + tty_buffer_free(tty, tty->buf.head);
>> + tty->buf.head = thead;
>
> This part of the change seems to have no effect at all. There are no
> locks held so there is nothing guaranteeing how the other processors
> views of the order of operations will be affected.
>
> Alan
>
Sorry, In you reply not all patch.
Main idea here - we never flash last (struct tty_buffer) in the active buffer.
Only data for ldisc. (tty->buf.head->read = tty->buf.head->commit).
At that moment driver can collect(write) data in buffer without conflict.
--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c
@@ -114,11 +114,14 @@ static void __tty_buffer_flush(struct tty_struct *tty)
{
struct tty_buffer *thead;
- while ((thead = tty->buf.head) != NULL) {
- tty->buf.head = thead->next;
- tty_buffer_free(tty, thead);
+ if (tty->buf.head == NULL)
+ return;
+ while ((thead = tty->buf.head->next) != NULL) {
+ tty_buffer_free(tty, tty->buf.head);
+ tty->buf.head = thead;
}
- tty->buf.tail = NULL;
+ WARN_ON(tty->buf.head != tty->buf.tail);
+ tty->buf.head->read = tty->buf.head->commit;
}
/**
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