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path: root/drivers/tty/n_tty.c
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Diffstat (limited to 'drivers/tty/n_tty.c')
-rw-r--r--drivers/tty/n_tty.c55
1 files changed, 32 insertions, 23 deletions
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index cbe98bc2b998..431742201709 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -124,6 +124,8 @@ struct n_tty_data {
struct mutex output_lock;
};
+#define MASK(x) ((x) & (N_TTY_BUF_SIZE - 1))
+
static inline size_t read_cnt(struct n_tty_data *ldata)
{
return ldata->read_head - ldata->read_tail;
@@ -141,6 +143,7 @@ static inline unsigned char *read_buf_addr(struct n_tty_data *ldata, size_t i)
static inline unsigned char echo_buf(struct n_tty_data *ldata, size_t i)
{
+ smp_rmb(); /* Matches smp_wmb() in add_echo_byte(). */
return ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
}
@@ -316,9 +319,7 @@ static inline void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
static void reset_buffer_flags(struct n_tty_data *ldata)
{
ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
- ldata->echo_head = ldata->echo_tail = ldata->echo_commit = 0;
ldata->commit_head = 0;
- ldata->echo_mark = 0;
ldata->line_start = 0;
ldata->erasing = 0;
@@ -617,13 +618,20 @@ static size_t __process_echoes(struct tty_struct *tty)
old_space = space = tty_write_room(tty);
tail = ldata->echo_tail;
- while (ldata->echo_commit != tail) {
+ while (MASK(ldata->echo_commit) != MASK(tail)) {
c = echo_buf(ldata, tail);
if (c == ECHO_OP_START) {
unsigned char op;
int no_space_left = 0;
/*
+ * Since add_echo_byte() is called without holding
+ * output_lock, we might see only portion of multi-byte
+ * operation.
+ */
+ if (MASK(ldata->echo_commit) == MASK(tail + 1))
+ goto not_yet_stored;
+ /*
* If the buffer byte is the start of a multi-byte
* operation, get the next byte, which is either the
* op code or a control character value.
@@ -634,6 +642,8 @@ static size_t __process_echoes(struct tty_struct *tty)
unsigned int num_chars, num_bs;
case ECHO_OP_ERASE_TAB:
+ if (MASK(ldata->echo_commit) == MASK(tail + 2))
+ goto not_yet_stored;
num_chars = echo_buf(ldata, tail + 2);
/*
@@ -728,7 +738,8 @@ static size_t __process_echoes(struct tty_struct *tty)
/* If the echo buffer is nearly full (so that the possibility exists
* of echo overrun before the next commit), then discard enough
* data at the tail to prevent a subsequent overrun */
- while (ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
+ while (ldata->echo_commit > tail &&
+ ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
if (echo_buf(ldata, tail) == ECHO_OP_START) {
if (echo_buf(ldata, tail + 1) == ECHO_OP_ERASE_TAB)
tail += 3;
@@ -738,6 +749,7 @@ static size_t __process_echoes(struct tty_struct *tty)
tail++;
}
+ not_yet_stored:
ldata->echo_tail = tail;
return old_space - space;
}
@@ -748,6 +760,7 @@ static void commit_echoes(struct tty_struct *tty)
size_t nr, old, echoed;
size_t head;
+ mutex_lock(&ldata->output_lock);
head = ldata->echo_head;
ldata->echo_mark = head;
old = ldata->echo_commit - ldata->echo_tail;
@@ -756,10 +769,12 @@ static void commit_echoes(struct tty_struct *tty)
* is over the threshold (and try again each time another
* block is accumulated) */
nr = head - ldata->echo_tail;
- if (nr < ECHO_COMMIT_WATERMARK || (nr % ECHO_BLOCK > old % ECHO_BLOCK))
+ if (nr < ECHO_COMMIT_WATERMARK ||
+ (nr % ECHO_BLOCK > old % ECHO_BLOCK)) {
+ mutex_unlock(&ldata->output_lock);
return;
+ }
- mutex_lock(&ldata->output_lock);
ldata->echo_commit = head;
echoed = __process_echoes(tty);
mutex_unlock(&ldata->output_lock);
@@ -810,7 +825,9 @@ static void flush_echoes(struct tty_struct *tty)
static inline void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
{
- *echo_buf_addr(ldata, ldata->echo_head++) = c;
+ *echo_buf_addr(ldata, ldata->echo_head) = c;
+ smp_wmb(); /* Matches smp_rmb() in echo_buf(). */
+ ldata->echo_head++;
}
/**
@@ -978,14 +995,15 @@ static void eraser(unsigned char c, struct tty_struct *tty)
}
seen_alnums = 0;
- while (ldata->read_head != ldata->canon_head) {
+ while (MASK(ldata->read_head) != MASK(ldata->canon_head)) {
head = ldata->read_head;
/* erase a single possibly multibyte character */
do {
head--;
c = read_buf(ldata, head);
- } while (is_continuation(c, tty) && head != ldata->canon_head);
+ } while (is_continuation(c, tty) &&
+ MASK(head) != MASK(ldata->canon_head));
/* do not partially erase */
if (is_continuation(c, tty))
@@ -1027,7 +1045,7 @@ static void eraser(unsigned char c, struct tty_struct *tty)
* This info is used to go back the correct
* number of columns.
*/
- while (tail != ldata->canon_head) {
+ while (MASK(tail) != MASK(ldata->canon_head)) {
tail--;
c = read_buf(ldata, tail);
if (c == '\t') {
@@ -1302,7 +1320,7 @@ n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
finish_erasing(ldata);
echo_char(c, tty);
echo_char_raw('\n', ldata);
- while (tail != ldata->read_head) {
+ while (MASK(tail) != MASK(ldata->read_head)) {
echo_char(read_buf(ldata, tail), tty);
tail++;
}
@@ -1878,30 +1896,21 @@ static int n_tty_open(struct tty_struct *tty)
struct n_tty_data *ldata;
/* Currently a malloc failure here can panic */
- ldata = vmalloc(sizeof(*ldata));
+ ldata = vzalloc(sizeof(*ldata));
if (!ldata)
- goto err;
+ return -ENOMEM;
ldata->overrun_time = jiffies;
mutex_init(&ldata->atomic_read_lock);
mutex_init(&ldata->output_lock);
tty->disc_data = ldata;
- reset_buffer_flags(tty->disc_data);
- ldata->column = 0;
- ldata->canon_column = 0;
- ldata->num_overrun = 0;
- ldata->no_room = 0;
- ldata->lnext = 0;
tty->closing = 0;
/* indicate buffer work may resume */
clear_bit(TTY_LDISC_HALTED, &tty->flags);
n_tty_set_termios(tty, NULL);
tty_unthrottle(tty);
-
return 0;
-err:
- return -ENOMEM;
}
static inline int input_available_p(struct tty_struct *tty, int poll)
@@ -2411,7 +2420,7 @@ static unsigned long inq_canon(struct n_tty_data *ldata)
tail = ldata->read_tail;
nr = head - tail;
/* Skip EOF-chars.. */
- while (head != tail) {
+ while (MASK(head) != MASK(tail)) {
if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
read_buf(ldata, tail) == __DISABLED_CHAR)
nr--;
generated by cgit v1.2.3 (git 2.39.1) at 2024-04-24 00:26:39 +0000