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terminal-util: switch from TCSADRAIN to TCSANOW for all tcsetattr() calls

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TCSADRAIN means tcsetattr() will become blocking (waiting for ability to
write out queued bytes), which is problematic, if the referenced TTY is
dead for some reason.

Since all these calls just modify *input* parameters anyway (i.e. mostly
local echo, and canonical mode), forcing out queued output is kinda
pointless anyway, hence just don't do it: leave it in the queue and just
change the flags we want to change.

The tcsetattr(3) man page kinda hints that we want to use TCSANOW here,
because it documents for TCSADRAIN:

"This option should be used when changing parameters that affect
output."

Which one can read so that TCSADRAIN should not be used if it doesn't
affect output, which is the case here.

This probably fixes: #37854
This commit is contained in:
Lennart Poettering
2025-06-26 01:24:52 +09:00
committed by Yu Watanabe
parent 9efffbbfde
commit f789b17e87
2 changed files with 14 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/basic/terminal-util.c
+12 -12
View File
@@ -122,18 +122,18 @@ int read_one_char(FILE *f, char *ret, usec_t t, bool echo, bool *need_nl) {
new_termios.c_cc[VMIN] = 1;
new_termios.c_cc[VTIME] = 0;
if (tcsetattr(fd, TCSADRAIN, &new_termios) >= 0) {
if (tcsetattr(fd, TCSANOW, &new_termios) >= 0) {
char c;
if (t != USEC_INFINITY) {
if (fd_wait_for_event(fd, POLLIN, t) <= 0) {
(void) tcsetattr(fd, TCSADRAIN, &old_termios);
(void) tcsetattr(fd, TCSANOW, &old_termios);
return -ETIMEDOUT;
}
}
r = safe_fgetc(f, &c);
(void) tcsetattr(fd, TCSADRAIN, &old_termios);
(void) tcsetattr(fd, TCSANOW, &old_termios);
if (r < 0)
return r;
if (r == 0)
@@ -323,7 +323,7 @@ int ask_string_full(
struct termios new_termios = old_termios;
termios_disable_echo(&new_termios);
if (tcsetattr(fd_input, TCSADRAIN, &new_termios) < 0)
if (tcsetattr(fd_input, TCSANOW, &new_termios) < 0)
return -errno;
for (;;) {
@@ -446,7 +446,7 @@ int ask_string_full(
fflush(stdout);
}
if (tcsetattr(fd_input, TCSADRAIN, &old_termios) < 0)
if (tcsetattr(fd_input, TCSANOW, &old_termios) < 0)
return -errno;
if (!string) {
@@ -459,7 +459,7 @@ int ask_string_full(
return 0;
fail:
(void) tcsetattr(fd_input, TCSADRAIN, &old_termios);
(void) tcsetattr(fd_input, TCSANOW, &old_termios);
return r;
fallback:
@@ -2105,7 +2105,7 @@ int get_default_background_color(double *ret_red, double *ret_green, double *ret
struct termios new_termios = old_termios;
termios_disable_echo(&new_termios);
if (tcsetattr(STDIN_FILENO, TCSADRAIN, &new_termios) < 0)
if (tcsetattr(STDIN_FILENO, TCSANOW, &new_termios) < 0)
return -errno;
r = loop_write(STDOUT_FILENO, ANSI_OSC "11;?" ANSI_ST, SIZE_MAX);
@@ -2177,7 +2177,7 @@ int get_default_background_color(double *ret_red, double *ret_green, double *ret
}
finish:
RET_GATHER(r, RET_NERRNO(tcsetattr(STDIN_FILENO, TCSADRAIN, &old_termios)));
RET_GATHER(r, RET_NERRNO(tcsetattr(STDIN_FILENO, TCSANOW, &old_termios)));
return r;
}
@@ -2302,7 +2302,7 @@ int terminal_get_size_by_dsr(
struct termios new_termios = old_termios;
termios_disable_echo(&new_termios);
if (tcsetattr(input_fd, TCSADRAIN, &new_termios) < 0)
if (tcsetattr(input_fd, TCSANOW, &new_termios) < 0)
return log_debug_errno(errno, "Failed to set new terminal settings: %m");
unsigned saved_row = 0, saved_column = 0;
@@ -2414,7 +2414,7 @@ finish:
if (saved_row > 0 && saved_column > 0)
RET_GATHER(r, terminal_set_cursor_position(output_fd, saved_row, saved_column));
RET_GATHER(r, RET_NERRNO(tcsetattr(input_fd, TCSADRAIN, &old_termios)));
RET_GATHER(r, RET_NERRNO(tcsetattr(input_fd, TCSANOW, &old_termios)));
return r;
}
@@ -2513,7 +2513,7 @@ int terminal_get_terminfo_by_dcs(int fd, char **ret_name) {
struct termios new_termios = old_termios;
termios_disable_echo(&new_termios);
if (tcsetattr(fd, TCSADRAIN, &new_termios) < 0)
if (tcsetattr(fd, TCSANOW, &new_termios) < 0)
return -errno;
r = loop_write(fd, DCS_TERMINFO_Q, SIZE_MAX);
@@ -2568,7 +2568,7 @@ int terminal_get_terminfo_by_dcs(int fd, char **ret_name) {
finish:
/* We ignore failure here. We already got a reply and if cleanup fails, we can't help that. */
(void) tcsetattr(fd, TCSADRAIN, &old_termios);
(void) tcsetattr(fd, TCSANOW, &old_termios);
return r;
}