From a88a69c91256418c5907c2f1f8a0ec0a36f9e6cc Mon Sep 17 00:00:00 2001 From: Joe Peterson Date: Fri, 2 Jan 2009 13:40:53 +0000 Subject: n_tty: Fix loss of echoed characters and remove bkl from n_tty Fixes the loss of echoed (and other ldisc-generated characters) when the tty is stopped or when the driver output buffer is full (happens frequently for input during continuous program output, such as ^C) and removes the Big Kernel Lock from the N_TTY line discipline. Adds an "echo buffer" to the N_TTY line discipline that handles all ldisc-generated output (including echoed characters). Along with the loss of characters, this also fixes the associated loss of sync between tty output and the ldisc state when characters cannot be immediately written to the tty driver. The echo buffer stores (in addition to characters) state operations that need to be done at the time of character output (like management of the column position). This allows echo to cooperate correctly with program output, since the ldisc state remains consistent with actual characters written. Since the echo buffer code now isolates the tty column state code to the process_out* and process_echoes functions, we can remove the Big Kernel Lock (BKL) and replace it with mutex locks. Highlights are: * Handles echo (and other ldisc output) when tty driver buffer is full - continuous program output can block echo * Saves echo when tty is in stopped state (e.g. ^S) - (e.g.: ^Q will correctly cause held characters to be released for output) * Control character pairs (e.g. "^C") are treated atomically and not split up by interleaved program output * Line discipline state is kept consistent with characters sent to the tty driver * Remove the big kernel lock (BKL) from N_TTY line discipline Signed-off-by: Joe Peterson Signed-off-by: Alan Cox Signed-off-by: Linus Torvalds --- drivers/char/n_tty.c | 736 ++++++++++++++++++++++++++++++++++++++++----------- 1 file changed, 584 insertions(+), 152 deletions(-) (limited to 'drivers/char/n_tty.c') diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c index efbfe9612658..a9bc5764fe75 100644 --- a/drivers/char/n_tty.c +++ b/drivers/char/n_tty.c @@ -62,6 +62,17 @@ #define TTY_THRESHOLD_THROTTLE 128 /* now based on remaining room */ #define TTY_THRESHOLD_UNTHROTTLE 128 +/* + * Special byte codes used in the echo buffer to represent operations + * or special handling of characters. Bytes in the echo buffer that + * are not part of such special blocks are treated as normal character + * codes. + */ +#define ECHO_OP_START 0xff +#define ECHO_OP_MOVE_BACK_COL 0x80 +#define ECHO_OP_SET_CANON_COL 0x81 +#define ECHO_OP_ERASE_TAB 0x82 + static inline unsigned char *alloc_buf(void) { gfp_t prio = in_interrupt() ? GFP_ATOMIC : GFP_KERNEL; @@ -169,6 +180,7 @@ static void check_unthrottle(struct tty_struct *tty) * * Locking: tty_read_lock for read fields. */ + static void reset_buffer_flags(struct tty_struct *tty) { unsigned long flags; @@ -176,6 +188,11 @@ static void reset_buffer_flags(struct tty_struct *tty) spin_lock_irqsave(&tty->read_lock, flags); tty->read_head = tty->read_tail = tty->read_cnt = 0; spin_unlock_irqrestore(&tty->read_lock, flags); + + mutex_lock(&tty->echo_lock); + tty->echo_pos = tty->echo_cnt = tty->echo_overrun = 0; + mutex_unlock(&tty->echo_lock); + tty->canon_head = tty->canon_data = tty->erasing = 0; memset(&tty->read_flags, 0, sizeof tty->read_flags); n_tty_set_room(tty); @@ -266,89 +283,116 @@ static inline int is_continuation(unsigned char c, struct tty_struct *tty) } /** - * opost - output post processor + * do_output_char - output one character * @c: character (or partial unicode symbol) * @tty: terminal device + * @space: space available in tty driver write buffer * - * Perform OPOST processing. Returns -1 when the output device is - * full and the character must be retried. Note that Linux currently - * ignores TABDLY, CRDLY, VTDLY, FFDLY and NLDLY. They simply aren't - * relevant in the world today. If you ever need them, add them here. + * This is a helper function that handles one output character + * (including special characters like TAB, CR, LF, etc.), + * putting the results in the tty driver's write buffer. + * + * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY + * and NLDLY. They simply aren't relevant in the world today. + * If you ever need them, add them here. * - * Called from both the receive and transmit sides and can be called - * re-entrantly. Relies on lock_kernel() for tty->column state. + * Returns the number of bytes of buffer space used or -1 if + * no space left. + * + * Locking: should be called under the output_lock to protect + * the column state and space left in the buffer */ -static int opost(unsigned char c, struct tty_struct *tty) +static int do_output_char(unsigned char c, struct tty_struct *tty, int space) { - int space, spaces; + int spaces; - space = tty_write_room(tty); if (!space) return -1; - - lock_kernel(); - if (O_OPOST(tty)) { - switch (c) { - case '\n': - if (O_ONLRET(tty)) - tty->column = 0; - if (O_ONLCR(tty)) { - if (space < 2) { - unlock_kernel(); - return -1; - } - tty_put_char(tty, '\r'); - tty->column = 0; - } - tty->canon_column = tty->column; - break; - case '\r': - if (O_ONOCR(tty) && tty->column == 0) { - unlock_kernel(); - return 0; - } - if (O_OCRNL(tty)) { - c = '\n'; - if (O_ONLRET(tty)) - tty->canon_column = tty->column = 0; - break; - } + + switch (c) { + case '\n': + if (O_ONLRET(tty)) + tty->column = 0; + if (O_ONLCR(tty)) { + if (space < 2) + return -1; tty->canon_column = tty->column = 0; + tty_put_char(tty, '\r'); + tty_put_char(tty, c); + return 2; + } + tty->canon_column = tty->column; + break; + case '\r': + if (O_ONOCR(tty) && tty->column == 0) + return 0; + if (O_OCRNL(tty)) { + c = '\n'; + if (O_ONLRET(tty)) + tty->canon_column = tty->column = 0; break; - case '\t': - spaces = 8 - (tty->column & 7); - if (O_TABDLY(tty) == XTABS) { - if (space < spaces) { - unlock_kernel(); - return -1; - } - tty->column += spaces; - tty->ops->write(tty, " ", spaces); - unlock_kernel(); - return 0; - } + } + tty->canon_column = tty->column = 0; + break; + case '\t': + spaces = 8 - (tty->column & 7); + if (O_TABDLY(tty) == XTABS) { + if (space < spaces) + return -1; tty->column += spaces; - break; - case '\b': - if (tty->column > 0) - tty->column--; - break; - default: - if (O_OLCUC(tty)) - c = toupper(c); - if (!iscntrl(c) && !is_continuation(c, tty)) - tty->column++; - break; + tty->ops->write(tty, " ", spaces); + return spaces; } + tty->column += spaces; + break; + case '\b': + if (tty->column > 0) + tty->column--; + break; + default: + if (O_OLCUC(tty)) + c = toupper(c); + if (!iscntrl(c) && !is_continuation(c, tty)) + tty->column++; + break; } + tty_put_char(tty, c); - unlock_kernel(); - return 0; + return 1; +} + +/** + * process_output - output post processor + * @c: character (or partial unicode symbol) + * @tty: terminal device + * + * Perform OPOST processing. Returns -1 when the output device is + * full and the character must be retried. + * + * Locking: output_lock to protect column state and space left + * (also, this is called from n_tty_write under the + * tty layer write lock) + */ + +static int process_output(unsigned char c, struct tty_struct *tty) +{ + int space, retval; + + mutex_lock(&tty->output_lock); + + space = tty_write_room(tty); + retval = do_output_char(c, tty, space); + + mutex_unlock(&tty->output_lock); + if (retval < 0) + return -1; + else + return 0; } /** - * opost_block - block postprocess + * process_output_block - block post processor * @tty: terminal device * @inbuf: user buffer * @nr: number of bytes @@ -358,24 +402,29 @@ static int opost(unsigned char c, struct tty_struct *tty) * the simple cases normally found and helps to generate blocks of * symbols for the console driver and thus improve performance. * - * Called from n_tty_write under the tty layer write lock. Relies - * on lock_kernel for the tty->column state. + * Locking: output_lock to protect column state and space left + * (also, this is called from n_tty_write under the + * tty layer write lock) */ -static ssize_t opost_block(struct tty_struct *tty, - const unsigned char *buf, unsigned int nr) +static ssize_t process_output_block(struct tty_struct *tty, + const unsigned char *buf, unsigned int nr) { int space; int i; const unsigned char *cp; + mutex_lock(&tty->output_lock); + space = tty_write_room(tty); if (!space) + { + mutex_unlock(&tty->output_lock); return 0; + } if (nr > space) nr = space; - lock_kernel(); for (i = 0, cp = buf; i < nr; i++, cp++) { switch (*cp) { case '\n': @@ -407,46 +456,393 @@ static ssize_t opost_block(struct tty_struct *tty, } } break_out: - if (tty->ops->flush_chars) - tty->ops->flush_chars(tty); i = tty->ops->write(tty, buf, i); - unlock_kernel(); + + mutex_unlock(&tty->output_lock); return i; } +/** + * process_echoes - write pending echo characters + * @tty: terminal device + * + * Write previously buffered echo (and other ldisc-generated) + * characters to the tty. + * + * Characters generated by the ldisc (including echoes) need to + * be buffered because the driver's write buffer can fill during + * heavy program output. Echoing straight to the driver will + * often fail under these conditions, causing lost characters and + * resulting mismatches of ldisc state information. + * + * Since the ldisc state must represent the characters actually sent + * to the driver at the time of the write, operations like certain + * changes in column state are also saved in the buffer and executed + * here. + * + * A circular fifo buffer is used so that the most recent characters + * are prioritized. Also, when control characters are echoed with a + * prefixed "^", the pair is treated atomically and thus not separated. + * + * Locking: output_lock to protect column state and space left, + * echo_lock to protect the echo buffer + */ + +static void process_echoes(struct tty_struct *tty) +{ + int space, nr; + unsigned char c; + unsigned char *cp, *buf_end; + + if (!tty->echo_cnt) + return; + + mutex_lock(&tty->output_lock); + mutex_lock(&tty->echo_lock); + + space = tty_write_room(tty); + + buf_end = tty->echo_buf + N_TTY_BUF_SIZE; + cp = tty->echo_buf + tty->echo_pos; + nr = tty->echo_cnt; + while (nr > 0) { + c = *cp; + if (c == ECHO_OP_START) { + unsigned char op; + unsigned char *opp; + int no_space_left = 0; + + /* + * 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. + */ + opp = cp + 1; + if (opp == buf_end) + opp -= N_TTY_BUF_SIZE; + op = *opp; + + switch (op) { + unsigned int num_chars, num_bs; + + case ECHO_OP_ERASE_TAB: + if (++opp == buf_end) + opp -= N_TTY_BUF_SIZE; + num_chars = *opp; + + /* + * Determine how many columns to go back + * in order to erase the tab. + * This depends on the number of columns + * used by other characters within the tab + * area. If this (modulo 8) count is from + * the start of input rather than from a + * previous tab, we offset by canon column. + * Otherwise, tab spacing is normal. + */ + if (!(num_chars & 0x80)) + num_chars += tty->canon_column; + num_bs = 8 - (num_chars & 7); + + if (num_bs > space) { + no_space_left = 1; + break; + } + space -= num_bs; + while (num_bs--) { + tty_put_char(tty, '\b'); + if (tty->column > 0) + tty->column--; + } + cp += 3; + nr -= 3; + break; + + case ECHO_OP_SET_CANON_COL: + tty->canon_column = tty->column; + cp += 2; + nr -= 2; + break; + + case ECHO_OP_MOVE_BACK_COL: + if (tty->column > 0) + tty->column--; + cp += 2; + nr -= 2; + break; + + case ECHO_OP_START: + /* This is an escaped echo op start code */ + if (!space) { + no_space_left = 1; + break; + } + tty_put_char(tty, ECHO_OP_START); + tty->column++; + space--; + cp += 2; + nr -= 2; + break; + + default: + if (iscntrl(op)) { + if (L_ECHOCTL(tty)) { + /* + * Ensure there is enough space + * for the whole ctrl pair. + */ + if (space < 2) { + no_space_left = 1; + break; + } + tty_put_char(tty, '^'); + tty_put_char(tty, op ^ 0100); + tty->column += 2; + space -= 2; + } else { + if (!space) { + no_space_left = 1; + break; + } + tty_put_char(tty, op); + space--; + } + } + /* + * If above falls through, this was an + * undefined op. + */ + cp += 2; + nr -= 2; + } + + if (no_space_left) + break; + } else { + int retval; + + if ((retval = do_output_char(c, tty, space)) < 0) + break; + space -= retval; + cp += 1; + nr -= 1; + } + + /* When end of circular buffer reached, wrap around */ + if (cp >= buf_end) + cp -= N_TTY_BUF_SIZE; + } + + if (nr == 0) { + tty->echo_pos = 0; + tty->echo_cnt = 0; + tty->echo_overrun = 0; + } else { + int num_processed = tty->echo_cnt - nr; + tty->echo_pos += num_processed; + tty->echo_pos &= N_TTY_BUF_SIZE - 1; + tty->echo_cnt = nr; + if (num_processed > 0) + tty->echo_overrun = 0; + } + + mutex_unlock(&tty->echo_lock); + mutex_unlock(&tty->output_lock); + + if (tty->ops->flush_chars) + tty->ops->flush_chars(tty); +} + +/** + * add_echo_byte - add a byte to the echo buffer + * @c: unicode byte to echo + * @tty: terminal device + * + * Add a character or operation byte to the echo buffer. + * + * Should be called under the echo lock to protect the echo buffer. + */ + +static void add_echo_byte(unsigned char c, struct tty_struct *tty) +{ + int new_byte_pos; + + if (tty->echo_cnt == N_TTY_BUF_SIZE) { + /* Circular buffer is already at capacity */ + new_byte_pos = tty->echo_pos; + + /* + * Since the buffer start position needs to be advanced, + * be sure to step by a whole operation byte group. + */ + if (tty->echo_buf[tty->echo_pos] == ECHO_OP_START) + { + if (tty->echo_buf[(tty->echo_pos + 1) & + (N_TTY_BUF_SIZE - 1)] == + ECHO_OP_ERASE_TAB) { + tty->echo_pos += 3; + tty->echo_cnt -= 2; + } else { + tty->echo_pos += 2; + tty->echo_cnt -= 1; + } + } else { + tty->echo_pos++; + } + tty->echo_pos &= N_TTY_BUF_SIZE - 1; + + tty->echo_overrun = 1; + } else { + new_byte_pos = tty->echo_pos + tty->echo_cnt; + new_byte_pos &= N_TTY_BUF_SIZE - 1; + tty->echo_cnt++; + } + + tty->echo_buf[new_byte_pos] = c; +} + +/** + * echo_move_back_col - add operation to move back a column + * @tty: terminal device + * + * Add an operation to the echo buffer to move back one column. + * + * Locking: echo_lock to protect the echo buffer + */ + +static void echo_move_back_col(struct tty_struct *tty) +{ + mutex_lock(&tty->echo_lock); + + add_echo_byte(ECHO_OP_START, tty); + add_echo_byte(ECHO_OP_MOVE_BACK_COL, tty); + + mutex_unlock(&tty->echo_lock); +} + +/** + * echo_set_canon_col - add operation to set the canon column + * @tty: terminal device + * + * Add an operation to the echo buffer to set the canon column + * to the current column. + * + * Locking: echo_lock to protect the echo buffer + */ + +static void echo_set_canon_col(struct tty_struct *tty) +{ + mutex_lock(&tty->echo_lock); + + add_echo_byte(ECHO_OP_START, tty); + add_echo_byte(ECHO_OP_SET_CANON_COL, tty); + + mutex_unlock(&tty->echo_lock); +} + +/** + * echo_erase_tab - add operation to erase a tab + * @num_chars: number of character columns already used + * @after_tab: true if num_chars starts after a previous tab + * @tty: terminal device + * + * Add an operation to the echo buffer to erase a tab. + * + * Called by the eraser function, which knows how many character + * columns have been used since either a previous tab or the start + * of input. This information will be used later, along with + * canon column (if applicable), to go back the correct number + * of columns. + * + * Locking: echo_lock to protect the echo buffer + */ + +static void echo_erase_tab(unsigned int num_chars, int after_tab, + struct tty_struct *tty) +{ + mutex_lock(&tty->echo_lock); + + add_echo_byte(ECHO_OP_START, tty); + add_echo_byte(ECHO_OP_ERASE_TAB, tty); + + /* We only need to know this modulo 8 (tab spacing) */ + num_chars &= 7; + + /* Set the high bit as a flag if num_chars is after a previous tab */ + if (after_tab) + num_chars |= 0x80; + + add_echo_byte(num_chars, tty); + + mutex_unlock(&tty->echo_lock); +} + +/** + * echo_char_raw - echo a character raw + * @c: unicode byte to echo + * @tty: terminal device + * + * Echo user input back onto the screen. This must be called only when + * L_ECHO(tty) is true. Called from the driver receive_buf path. + * + * This variant does not treat control characters specially. + * + * Locking: echo_lock to protect the echo buffer + */ + +static void echo_char_raw(unsigned char c, struct tty_struct *tty) +{ + mutex_lock(&tty->echo_lock); + + if (c == ECHO_OP_START) { + add_echo_byte(ECHO_OP_START, tty); + add_echo_byte(ECHO_OP_START, tty); + } else { + add_echo_byte(c, tty); + } + + mutex_unlock(&tty->echo_lock); +} /** - * echo_char - echo characters + * echo_char - echo a character * @c: unicode byte to echo * @tty: terminal device * * Echo user input back onto the screen. This must be called only when * L_ECHO(tty) is true. Called from the driver receive_buf path. * - * Relies on BKL for tty column locking + * This variant tags control characters to be possibly echoed as + * as "^X" (where X is the letter representing the control char). + * + * Locking: echo_lock to protect the echo buffer */ static void echo_char(unsigned char c, struct tty_struct *tty) { - if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t') { - tty_put_char(tty, '^'); - tty_put_char(tty, c ^ 0100); - tty->column += 2; - } else - opost(c, tty); + mutex_lock(&tty->echo_lock); + + if (c == ECHO_OP_START) { + add_echo_byte(ECHO_OP_START, tty); + add_echo_byte(ECHO_OP_START, tty); + } else { + if (iscntrl(c) && c != '\t') + add_echo_byte(ECHO_OP_START, tty); + add_echo_byte(c, tty); + } + + mutex_unlock(&tty->echo_lock); } /** - * finsh_erasing - complete erase + * finish_erasing - complete erase * @tty: tty doing the erase - * - * Relies on BKL for tty column locking */ + static inline void finish_erasing(struct tty_struct *tty) { if (tty->erasing) { - tty_put_char(tty, '/'); - tty->column++; + echo_char_raw('/', tty); tty->erasing = 0; } } @@ -460,7 +856,7 @@ static inline void finish_erasing(struct tty_struct *tty) * present in the stream from the driver layer. Handles the complexities * of UTF-8 multibyte symbols. * - * Locking: read_lock for tty buffers, BKL for column/erasing state + * Locking: read_lock for tty buffers */ static void eraser(unsigned char c, struct tty_struct *tty) @@ -471,7 +867,7 @@ static void eraser(unsigned char c, struct tty_struct *tty) /* FIXME: locking needed ? */ if (tty->read_head == tty->canon_head) { - /* opost('\a', tty); */ /* what do you think? */ + /* echo_char_raw('\a', tty); */ /* what do you think? */ return; } if (c == ERASE_CHAR(tty)) @@ -497,7 +893,7 @@ static void eraser(unsigned char c, struct tty_struct *tty) echo_char(KILL_CHAR(tty), tty); /* Add a newline if ECHOK is on and ECHOKE is off. */ if (L_ECHOK(tty)) - opost('\n', tty); + echo_char_raw('\n', tty); return; } kill_type = KILL; @@ -533,67 +929,62 @@ static void eraser(unsigned char c, struct tty_struct *tty) if (L_ECHO(tty)) { if (L_ECHOPRT(tty)) { if (!tty->erasing) { - tty_put_char(tty, '\\'); - tty->column++; + echo_char_raw('\\', tty); tty->erasing = 1; } /* if cnt > 1, output a multi-byte character */ echo_char(c, tty); while (--cnt > 0) { head = (head+1) & (N_TTY_BUF_SIZE-1); - tty_put_char(tty, tty->read_buf[head]); + echo_char_raw(tty->read_buf[head], tty); + echo_move_back_col(tty); } } else if (kill_type == ERASE && !L_ECHOE(tty)) { echo_char(ERASE_CHAR(tty), tty); } else if (c == '\t') { - unsigned int col = tty->canon_column; - unsigned long tail = tty->canon_head; - - /* Find the column of the last char. */ - while (tail != tty->read_head) { + unsigned int num_chars = 0; + int after_tab = 0; + unsigned long tail = tty->read_head; + + /* + * Count the columns used for characters + * since the start of input or after a + * previous tab. + * This info is used to go back the correct + * number of columns. + */ + while (tail != tty->canon_head) { + tail = (tail-1) & (N_TTY_BUF_SIZE-1); c = tty->read_buf[tail]; - if (c == '\t') - col = (col | 7) + 1; + if (c == '\t') { + after_tab = 1; + break; + } else if (iscntrl(c)) { if (L_ECHOCTL(tty)) - col += 2; - } else if (!is_continuation(c, tty)) - col++; - tail = (tail+1) & (N_TTY_BUF_SIZE-1); - } - - /* should never happen */ - if (tty->column > 0x80000000) - tty->column = 0; - - /* Now backup to that column. */ - while (tty->column > col) { - /* Can't use opost here. */ - tty_put_char(tty, '\b'); - if (tty->column > 0) - tty->column--; + num_chars += 2; + } else if (!is_continuation(c, tty)) { + num_chars++; + } } + echo_erase_tab(num_chars, after_tab, tty); } else { if (iscntrl(c) && L_ECHOCTL(tty)) { - tty_put_char(tty, '\b'); - tty_put_char(tty, ' '); - tty_put_char(tty, '\b'); - if (tty->column > 0) - tty->column--; + echo_char_raw('\b', tty); + echo_char_raw(' ', tty); + echo_char_raw('\b', tty); } if (!iscntrl(c) || L_ECHOCTL(tty)) { - tty_put_char(tty, '\b'); - tty_put_char(tty, ' '); - tty_put_char(tty, '\b'); - if (tty->column > 0) - tty->column--; + echo_char_raw('\b', tty); + echo_char_raw(' ', tty); + echo_char_raw('\b', tty); } } } if (kill_type == ERASE) break; } - if (tty->read_head == tty->canon_head) + if (tty->read_head == tty->canon_head && L_ECHO(tty)) finish_erasing(tty); } @@ -724,14 +1115,18 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c) c=tolower(c); if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && - ((I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty)) || - c == INTR_CHAR(tty) || c == QUIT_CHAR(tty) || c == SUSP_CHAR(tty))) + I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty) && + c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) && c != SUSP_CHAR(tty)) { start_tty(tty); + process_echoes(tty); + } if (tty->closing) { if (I_IXON(tty)) { - if (c == START_CHAR(tty)) + if (c == START_CHAR(tty)) { start_tty(tty); + process_echoes(tty); + } else if (c == STOP_CHAR(tty)) stop_tty(tty); } @@ -745,17 +1140,20 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c) * up. */ if (!test_bit(c, tty->process_char_map) || tty->lnext) { - finish_erasing(tty); tty->lnext = 0; if (L_ECHO(tty)) { + finish_erasing(tty); if (tty->read_cnt >= N_TTY_BUF_SIZE-1) { - tty_put_char(tty, '\a'); /* beep if no space */ + /* beep if no space */ + echo_char_raw('\a', tty); + process_echoes(tty); return; } /* Record the column of first canon char. */ if (tty->canon_head == tty->read_head) - tty->canon_column = tty->column; + echo_set_canon_col(tty); echo_char(c, tty); + process_echoes(tty); } if (I_PARMRK(tty) && c == (unsigned char) '\377') put_tty_queue(c, tty); @@ -766,6 +1164,7 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c) if (I_IXON(tty)) { if (c == START_CHAR(tty)) { start_tty(tty); + process_echoes(tty); return; } if (c == STOP_CHAR(tty)) { @@ -786,7 +1185,6 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c) if (c == SUSP_CHAR(tty)) { send_signal: /* - * Echo character, and then send the signal. * Note that we do not use isig() here because we want * the order to be: * 1) flush, 2) echo, 3) signal @@ -795,8 +1193,12 @@ send_signal: n_tty_flush_buffer(tty); tty_driver_flush_buffer(tty); } - if (L_ECHO(tty)) + if (I_IXON(tty)) + start_tty(tty); + if (L_ECHO(tty)) { echo_char(c, tty); + process_echoes(tty); + } if (tty->pgrp) kill_pgrp(tty->pgrp, signal, 1); return; @@ -815,6 +1217,7 @@ send_signal: if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) || (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) { eraser(c, tty); + process_echoes(tty); return; } if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) { @@ -822,8 +1225,9 @@ send_signal: if (L_ECHO(tty)) { finish_erasing(tty); if (L_ECHOCTL(tty)) { - tty_put_char(tty, '^'); - tty_put_char(tty, '\b'); + echo_char_raw('^', tty); + echo_char_raw('\b', tty); + process_echoes(tty); } } return; @@ -834,18 +1238,20 @@ send_signal: finish_erasing(tty); echo_char(c, tty); - opost('\n', tty); + echo_char_raw('\n', tty); while (tail != tty->read_head) { echo_char(tty->read_buf[tail], tty); tail = (tail+1) & (N_TTY_BUF_SIZE-1); } + process_echoes(tty); return; } if (c == '\n') { if (L_ECHO(tty) || L_ECHONL(tty)) { if (tty->read_cnt >= N_TTY_BUF_SIZE-1) - tty_put_char(tty, '\a'); - opost('\n', tty); + echo_char_raw('\a', tty); + echo_char_raw('\n', tty); + process_echoes(tty); } goto handle_newline; } @@ -862,11 +1268,12 @@ send_signal: */ if (L_ECHO(tty)) { if (tty->read_cnt >= N_TTY_BUF_SIZE-1) - tty_put_char(tty, '\a'); + echo_char_raw('\a', tty); /* Record the column of first canon char. */ if (tty->canon_head == tty->read_head) - tty->canon_column = tty->column; + echo_set_canon_col(tty); echo_char(c, tty); + process_echoes(tty); } /* * XXX does PARMRK doubling happen for @@ -889,20 +1296,23 @@ handle_newline: } } - finish_erasing(tty); if (L_ECHO(tty)) { + finish_erasing(tty); if (tty->read_cnt >= N_TTY_BUF_SIZE-1) { - tty_put_char(tty, '\a'); /* beep if no space */ + /* beep if no space */ + echo_char_raw('\a', tty); + process_echoes(tty); return; } if (c == '\n') - opost('\n', tty); + echo_char_raw('\n', tty); else { /* Record the column of first canon char. */ if (tty->canon_head == tty->read_head) - tty->canon_column = tty->column; + echo_set_canon_col(tty); echo_char(c, tty); } + process_echoes(tty); } if (I_PARMRK(tty) && c == (unsigned char) '\377') @@ -923,6 +1333,9 @@ handle_newline: static void n_tty_write_wakeup(struct tty_struct *tty) { + /* Write out any echoed characters that are still pending */ + process_echoes(tty); + if (tty->fasync) { set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); kill_fasync(&tty->fasync, SIGIO, POLL_OUT); @@ -1134,6 +1547,10 @@ static void n_tty_close(struct tty_struct *tty) free_buf(tty->read_buf); tty->read_buf = NULL; } + if (tty->echo_buf) { + free_buf(tty->echo_buf); + tty->echo_buf = NULL; + } } /** @@ -1151,13 +1568,19 @@ static int n_tty_open(struct tty_struct *tty) if (!tty) return -EINVAL; - /* This one is ugly. Currently a malloc failure here can panic */ + /* These are ugly. Currently a malloc failure here can panic */ if (!tty->read_buf) { tty->read_buf = alloc_buf(); if (!tty->read_buf) return -ENOMEM; } + if (!tty->echo_buf) { + tty->echo_buf = alloc_buf(); + if (!tty->echo_buf) + return -ENOMEM; + } memset(tty->read_buf, 0, N_TTY_BUF_SIZE); + memset(tty->echo_buf, 0, N_TTY_BUF_SIZE); reset_buffer_flags(tty); tty->column = 0; n_tty_set_termios(tty, NULL); @@ -1487,16 +1910,23 @@ do_it_again: * @buf: userspace buffer pointer * @nr: size of I/O * - * Write function of the terminal device. This is serialized with + * Write function of the terminal device. This is serialized with * respect to other write callers but not to termios changes, reads - * and other such events. We must be careful with N_TTY as the receive - * code will echo characters, thus calling driver write methods. + * and other such events. Since the receive code will echo characters, + * thus calling driver write methods, the output_lock is used in + * the output processing functions called here as well as in the + * echo processing function to protect the column state and space + * left in the buffer. * * This code must be sure never to sleep through a hangup. + * + * Locking: output_lock to protect column state and space left + * (note that the process_output*() functions take this + * lock themselves) */ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file, - const unsigned char *buf, size_t nr) + const unsigned char *buf, size_t nr) { const unsigned char *b = buf; DECLARE_WAITQUEUE(wait, current); @@ -1510,6 +1940,9 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file, return retval; } + /* Write out any echoed characters that are still pending */ + process_echoes(tty); + add_wait_queue(&tty->write_wait, &wait); while (1) { set_current_state(TASK_INTERRUPTIBLE); @@ -1523,7 +1956,7 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file, } if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) { while (nr > 0) { - ssize_t num = opost_block(tty, b, nr); + ssize_t num = process_output_block(tty, b, nr); if (num < 0) { if (num == -EAGAIN) break; @@ -1535,7 +1968,7 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file, if (nr == 0) break; c = *b; - if (opost(c, tty) < 0) + if (process_output(c, tty) < 0) break; b++; nr--; } @@ -1663,4 +2096,3 @@ struct tty_ldisc_ops tty_ldisc_N_TTY = { .receive_buf = n_tty_receive_buf, .write_wakeup = n_tty_write_wakeup }; - -- cgit v1.2.3 From 300a6204b4d45dc70359b24384ad04ae899179c3 Mon Sep 17 00:00:00 2001 From: Alan Cox Date: Fri, 2 Jan 2009 13:41:04 +0000 Subject: n_tty: clean up coding style Now the main work is done its polishing time Signed-off-by: Alan Cox Signed-off-by: Linus Torvalds --- drivers/char/n_tty.c | 29 +++++++++++++---------------- 1 file changed, 13 insertions(+), 16 deletions(-) (limited to 'drivers/char/n_tty.c') diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c index a9bc5764fe75..a223823544bf 100644 --- a/drivers/char/n_tty.c +++ b/drivers/char/n_tty.c @@ -47,8 +47,8 @@ #include #include #include +#include -#include #include /* number of characters left in xmit buffer before select has we have room */ @@ -309,7 +309,7 @@ static int do_output_char(unsigned char c, struct tty_struct *tty, int space) if (!space) return -1; - + switch (c) { case '\n': if (O_ONLRET(tty)) @@ -417,8 +417,7 @@ static ssize_t process_output_block(struct tty_struct *tty, mutex_lock(&tty->output_lock); space = tty_write_room(tty); - if (!space) - { + if (!space) { mutex_unlock(&tty->output_lock); return 0; } @@ -521,7 +520,7 @@ static void process_echoes(struct tty_struct *tty) if (opp == buf_end) opp -= N_TTY_BUF_SIZE; op = *opp; - + switch (op) { unsigned int num_chars, num_bs; @@ -621,7 +620,8 @@ static void process_echoes(struct tty_struct *tty) } else { int retval; - if ((retval = do_output_char(c, tty, space)) < 0) + retval = do_output_char(c, tty, space); + if (retval < 0) break; space -= retval; cp += 1; @@ -675,8 +675,7 @@ static void add_echo_byte(unsigned char c, struct tty_struct *tty) * Since the buffer start position needs to be advanced, * be sure to step by a whole operation byte group. */ - if (tty->echo_buf[tty->echo_pos] == ECHO_OP_START) - { + if (tty->echo_buf[tty->echo_pos] == ECHO_OP_START) { if (tty->echo_buf[(tty->echo_pos + 1) & (N_TTY_BUF_SIZE - 1)] == ECHO_OP_ERASE_TAB) { @@ -771,7 +770,7 @@ static void echo_erase_tab(unsigned int num_chars, int after_tab, /* Set the high bit as a flag if num_chars is after a previous tab */ if (after_tab) num_chars |= 0x80; - + add_echo_byte(num_chars, tty); mutex_unlock(&tty->echo_lock); @@ -959,8 +958,7 @@ static void eraser(unsigned char c, struct tty_struct *tty) if (c == '\t') { after_tab = 1; break; - } - else if (iscntrl(c)) { + } else if (iscntrl(c)) { if (L_ECHOCTL(tty)) num_chars += 2; } else if (!is_continuation(c, tty)) { @@ -1112,7 +1110,7 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c) if (I_ISTRIP(tty)) c &= 0x7f; if (I_IUCLC(tty) && L_IEXTEN(tty)) - c=tolower(c); + c = tolower(c); if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty) && @@ -1126,8 +1124,7 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c) if (c == START_CHAR(tty)) { start_tty(tty); process_echoes(tty); - } - else if (c == STOP_CHAR(tty)) + } else if (c == STOP_CHAR(tty)) stop_tty(tty); } return; @@ -1335,7 +1332,7 @@ static void n_tty_write_wakeup(struct tty_struct *tty) { /* Write out any echoed characters that are still pending */ process_echoes(tty); - + if (tty->fasync) { set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); kill_fasync(&tty->fasync, SIGIO, POLL_OUT); @@ -1942,7 +1939,7 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file, /* Write out any echoed characters that are still pending */ process_echoes(tty); - + add_wait_queue(&tty->write_wait, &wait); while (1) { set_current_state(TASK_INTERRUPTIBLE); -- cgit v1.2.3 From a59c0d6f14315a3f300f6f3786137213727e4c47 Mon Sep 17 00:00:00 2001 From: Joe Peterson Date: Fri, 2 Jan 2009 13:43:25 +0000 Subject: n_tty: Fix handling of control characters and continuations Fix process_output_block to detect continuation characters correctly and to handle control characters even when O_OLCUC is enabled. Make similar change to do_output_char(). Signed-off-by: Joe Peterson Signed-off-by: Alan Cox Signed-off-by: Linus Torvalds --- drivers/char/n_tty.c | 24 +++++++++++++++--------- 1 file changed, 15 insertions(+), 9 deletions(-) (limited to 'drivers/char/n_tty.c') diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c index a223823544bf..30b0426b3788 100644 --- a/drivers/char/n_tty.c +++ b/drivers/char/n_tty.c @@ -351,10 +351,12 @@ static int do_output_char(unsigned char c, struct tty_struct *tty, int space) tty->column--; break; default: - if (O_OLCUC(tty)) - c = toupper(c); - if (!iscntrl(c) && !is_continuation(c, tty)) - tty->column++; + if (!iscntrl(c)) { + if (O_OLCUC(tty)) + c = toupper(c); + if (!is_continuation(c, tty)) + tty->column++; + } break; } @@ -425,7 +427,9 @@ static ssize_t process_output_block(struct tty_struct *tty, nr = space; for (i = 0, cp = buf; i < nr; i++, cp++) { - switch (*cp) { + unsigned char c = *cp; + + switch (c) { case '\n': if (O_ONLRET(tty)) tty->column = 0; @@ -447,10 +451,12 @@ static ssize_t process_output_block(struct tty_struct *tty, tty->column--; break; default: - if (O_OLCUC(tty)) - goto break_out; - if (!iscntrl(*cp)) - tty->column++; + if (!iscntrl(c)) { + if (O_OLCUC(tty)) + goto break_out; + if (!is_continuation(c, tty)) + tty->column++; + } break; } } -- cgit v1.2.3 From acc71bbad33478973dbed68ebbc2d76dac9a51bd Mon Sep 17 00:00:00 2001 From: Joe Peterson Date: Fri, 2 Jan 2009 13:43:32 +0000 Subject: n_tty: Fix hanfling of buffer full corner cases Fix the handling of input characters when the tty buffer is full or nearly full. This includes tests that are done in n_tty_receive_char() and handling of PARMRK. Problems with the buffer-full tests done in receive_char() caused characters to be lost at times when the buffer(s) filled. Also, these full conditions would often only be detected with echo on, and PARMRK was not accounted for properly in all cases. One symptom of these problems, in addition to lost characters, was early termination from unix commands like tr and cat when ^Q was used to break from a stopped tty with full buffers (note that breaking out was often previously not possible, due to the pty getting in "gridlock", which will be addressed in another patch). Note space is always reserved at the end of the buffer for a newline (or EOF/EOL) in canonical mode. Signed-off-by: Joe Peterson Signed-off-by: Alan Cox Signed-off-by: Linus Torvalds --- drivers/char/n_tty.c | 55 ++++++++++++++++++++++++++++++++++++---------------- 1 file changed, 38 insertions(+), 17 deletions(-) (limited to 'drivers/char/n_tty.c') diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c index 30b0426b3788..4b1e96b65ab0 100644 --- a/drivers/char/n_tty.c +++ b/drivers/char/n_tty.c @@ -1107,6 +1107,7 @@ static inline void n_tty_receive_parity_error(struct tty_struct *tty, static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c) { unsigned long flags; + int parmrk; if (tty->raw) { put_tty_queue(c, tty); @@ -1144,21 +1145,24 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c) */ if (!test_bit(c, tty->process_char_map) || tty->lnext) { tty->lnext = 0; - if (L_ECHO(tty)) { - finish_erasing(tty); - if (tty->read_cnt >= N_TTY_BUF_SIZE-1) { - /* beep if no space */ + parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0; + if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) { + /* beep if no space */ + if (L_ECHO(tty)) { echo_char_raw('\a', tty); process_echoes(tty); - return; } + return; + } + if (L_ECHO(tty)) { + finish_erasing(tty); /* Record the column of first canon char. */ if (tty->canon_head == tty->read_head) echo_set_canon_col(tty); echo_char(c, tty); process_echoes(tty); } - if (I_PARMRK(tty) && c == (unsigned char) '\377') + if (parmrk) put_tty_queue(c, tty); put_tty_queue(c, tty); return; @@ -1250,15 +1254,22 @@ send_signal: return; } if (c == '\n') { - if (L_ECHO(tty) || L_ECHONL(tty)) { - if (tty->read_cnt >= N_TTY_BUF_SIZE-1) + if (tty->read_cnt >= N_TTY_BUF_SIZE) { + if (L_ECHO(tty)) { echo_char_raw('\a', tty); + process_echoes(tty); + } + return; + } + if (L_ECHO(tty) || L_ECHONL(tty)) { echo_char_raw('\n', tty); process_echoes(tty); } goto handle_newline; } if (c == EOF_CHAR(tty)) { + if (tty->read_cnt >= N_TTY_BUF_SIZE) + return; if (tty->canon_head != tty->read_head) set_bit(TTY_PUSH, &tty->flags); c = __DISABLED_CHAR; @@ -1266,12 +1277,19 @@ send_signal: } if ((c == EOL_CHAR(tty)) || (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) { + parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) + ? 1 : 0; + if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk)) { + if (L_ECHO(tty)) { + echo_char_raw('\a', tty); + process_echoes(tty); + } + return; + } /* * XXX are EOL_CHAR and EOL2_CHAR echoed?!? */ if (L_ECHO(tty)) { - if (tty->read_cnt >= N_TTY_BUF_SIZE-1) - echo_char_raw('\a', tty); /* Record the column of first canon char. */ if (tty->canon_head == tty->read_head) echo_set_canon_col(tty); @@ -1282,7 +1300,7 @@ send_signal: * XXX does PARMRK doubling happen for * EOL_CHAR and EOL2_CHAR? */ - if (I_PARMRK(tty) && c == (unsigned char) '\377') + if (parmrk) put_tty_queue(c, tty); handle_newline: @@ -1299,14 +1317,17 @@ handle_newline: } } - if (L_ECHO(tty)) { - finish_erasing(tty); - if (tty->read_cnt >= N_TTY_BUF_SIZE-1) { - /* beep if no space */ + parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0; + if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) { + /* beep if no space */ + if (L_ECHO(tty)) { echo_char_raw('\a', tty); process_echoes(tty); - return; } + return; + } + if (L_ECHO(tty)) { + finish_erasing(tty); if (c == '\n') echo_char_raw('\n', tty); else { @@ -1318,7 +1339,7 @@ handle_newline: process_echoes(tty); } - if (I_PARMRK(tty) && c == (unsigned char) '\377') + if (parmrk) put_tty_queue(c, tty); put_tty_queue(c, tty); -- cgit v1.2.3 From 7e94b1d9bffc18dca3b45554d9d118a3ffcc4d1b Mon Sep 17 00:00:00 2001 From: Joe Peterson Date: Fri, 2 Jan 2009 13:43:40 +0000 Subject: n_tty: Output bells immediately on a full buffer This patch causes "bell" (^G) characters (invoked when the input buffer is full) to be immediately output rather than filling the echo buffer. This is especially a problem when the tty is stopped and buffers fill, since the bells do not serve their purpose of immediate notification that the buffer cannot take further input, and they will flush all at once when the tty is restarted. Signed-off-by: Joe Peterson Signed-off-by: Alan Cox Signed-off-by: Linus Torvalds --- drivers/char/n_tty.c | 26 +++++++++----------------- 1 file changed, 9 insertions(+), 17 deletions(-) (limited to 'drivers/char/n_tty.c') diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c index 4b1e96b65ab0..3922a084205e 100644 --- a/drivers/char/n_tty.c +++ b/drivers/char/n_tty.c @@ -872,7 +872,7 @@ static void eraser(unsigned char c, struct tty_struct *tty) /* FIXME: locking needed ? */ if (tty->read_head == tty->canon_head) { - /* echo_char_raw('\a', tty); */ /* what do you think? */ + /* process_output('\a', tty); */ /* what do you think? */ return; } if (c == ERASE_CHAR(tty)) @@ -1148,10 +1148,8 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c) parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0; if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) { /* beep if no space */ - if (L_ECHO(tty)) { - echo_char_raw('\a', tty); - process_echoes(tty); - } + if (L_ECHO(tty)) + process_output('\a', tty); return; } if (L_ECHO(tty)) { @@ -1255,10 +1253,8 @@ send_signal: } if (c == '\n') { if (tty->read_cnt >= N_TTY_BUF_SIZE) { - if (L_ECHO(tty)) { - echo_char_raw('\a', tty); - process_echoes(tty); - } + if (L_ECHO(tty)) + process_output('\a', tty); return; } if (L_ECHO(tty) || L_ECHONL(tty)) { @@ -1280,10 +1276,8 @@ send_signal: parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0; if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk)) { - if (L_ECHO(tty)) { - echo_char_raw('\a', tty); - process_echoes(tty); - } + if (L_ECHO(tty)) + process_output('\a', tty); return; } /* @@ -1320,10 +1314,8 @@ handle_newline: parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0; if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) { /* beep if no space */ - if (L_ECHO(tty)) { - echo_char_raw('\a', tty); - process_echoes(tty); - } + if (L_ECHO(tty)) + process_output('\a', tty); return; } if (L_ECHO(tty)) { -- cgit v1.2.3 From ff8cb0fd6f195389aefe55d5dac9927d09a9de54 Mon Sep 17 00:00:00 2001 From: Thomas Pfaff Date: Fri, 2 Jan 2009 13:47:13 +0000 Subject: tty: N_TTY SIGIO only works for read The N_TTY ldisc layer does not send SIGIO POLL_OUTs correctly when output is possible due to flawed handling of the TTY_DO_WRITE_WAKEUP bit. It will either send no SIGIOs at all or on every tty wakeup. The fix is to set the bit when the tty driver write would block and test and clear it on write wakeup. [Merged with existing N_TTY patches and a small buglet fixed -- Alan] Signed-off-by: Thomas Pfaff Signed-off-by: Alan Cox Signed-off-by: Linus Torvalds --- drivers/char/n_tty.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'drivers/char/n_tty.c') diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c index 3922a084205e..f6f0e4ec2b51 100644 --- a/drivers/char/n_tty.c +++ b/drivers/char/n_tty.c @@ -1352,10 +1352,8 @@ static void n_tty_write_wakeup(struct tty_struct *tty) /* Write out any echoed characters that are still pending */ process_echoes(tty); - if (tty->fasync) { - set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); + if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) kill_fasync(&tty->fasync, SIGIO, POLL_OUT); - } } /** @@ -2014,6 +2012,8 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file, break_out: __set_current_state(TASK_RUNNING); remove_wait_queue(&tty->write_wait, &wait); + if (b - buf != nr && tty->fasync) + set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); return (b - buf) ? b - buf : retval; } -- cgit v1.2.3