aboutsummaryrefslogtreecommitdiffstats
path: root/drivers
diff options
context:
space:
mode:
authorPeter Zijlstra <peterz@infradead.org>2014-09-24 04:18:51 -0400
committerIngo Molnar <mingo@kernel.org>2014-10-28 05:56:10 -0400
commit97d9e28d1a27b84a6a0b155f2390289afa279341 (patch)
tree795f01ef74c97cb2397f0abddb17234c0b264b75 /drivers
parente23738a7300a7591a57a22f47b813fd1b53ec404 (diff)
sched, tty: Deal with nested sleeps
n_tty_{read,write} are wait loops with sleeps in. Wait loops rely on task_struct::state and sleeps do too, since that's the only means of actually sleeping. Therefore the nested sleeps destroy the wait loop state. Fix this by using the new woken_wake_function and wait_woken() stuff, which registers wakeups in wait and thereby allows shrinking the task_state::state changes to the actual sleep part. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: tglx@linutronix.de Cc: ilya.dryomov@inktank.com Cc: umgwanakikbuti@gmail.com Cc: oleg@redhat.com Link: http://lkml.kernel.org/r/20140924082242.323011233@infradead.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/tty/n_tty.c17
1 files changed, 5 insertions, 12 deletions
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 89c4cee253e3..fb3f519b803f 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -2123,7 +2123,7 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
2123{ 2123{
2124 struct n_tty_data *ldata = tty->disc_data; 2124 struct n_tty_data *ldata = tty->disc_data;
2125 unsigned char __user *b = buf; 2125 unsigned char __user *b = buf;
2126 DECLARE_WAITQUEUE(wait, current); 2126 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2127 int c; 2127 int c;
2128 int minimum, time; 2128 int minimum, time;
2129 ssize_t retval = 0; 2129 ssize_t retval = 0;
@@ -2186,10 +2186,6 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
2186 nr--; 2186 nr--;
2187 break; 2187 break;
2188 } 2188 }
2189 /* This statement must be first before checking for input
2190 so that any interrupt will set the state back to
2191 TASK_RUNNING. */
2192 set_current_state(TASK_INTERRUPTIBLE);
2193 2189
2194 if (((minimum - (b - buf)) < ldata->minimum_to_wake) && 2190 if (((minimum - (b - buf)) < ldata->minimum_to_wake) &&
2195 ((minimum - (b - buf)) >= 1)) 2191 ((minimum - (b - buf)) >= 1))
@@ -2220,13 +2216,13 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
2220 n_tty_set_room(tty); 2216 n_tty_set_room(tty);
2221 up_read(&tty->termios_rwsem); 2217 up_read(&tty->termios_rwsem);
2222 2218
2223 timeout = schedule_timeout(timeout); 2219 timeout = wait_woken(&wait, TASK_INTERRUPTIBLE,
2220 timeout);
2224 2221
2225 down_read(&tty->termios_rwsem); 2222 down_read(&tty->termios_rwsem);
2226 continue; 2223 continue;
2227 } 2224 }
2228 } 2225 }
2229 __set_current_state(TASK_RUNNING);
2230 2226
2231 /* Deal with packet mode. */ 2227 /* Deal with packet mode. */
2232 if (packet && b == buf) { 2228 if (packet && b == buf) {
@@ -2273,7 +2269,6 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
2273 2269
2274 mutex_unlock(&ldata->atomic_read_lock); 2270 mutex_unlock(&ldata->atomic_read_lock);
2275 2271
2276 __set_current_state(TASK_RUNNING);
2277 if (b - buf) 2272 if (b - buf)
2278 retval = b - buf; 2273 retval = b - buf;
2279 2274
@@ -2306,7 +2301,7 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2306 const unsigned char *buf, size_t nr) 2301 const unsigned char *buf, size_t nr)
2307{ 2302{
2308 const unsigned char *b = buf; 2303 const unsigned char *b = buf;
2309 DECLARE_WAITQUEUE(wait, current); 2304 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2310 int c; 2305 int c;
2311 ssize_t retval = 0; 2306 ssize_t retval = 0;
2312 2307
@@ -2324,7 +2319,6 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2324 2319
2325 add_wait_queue(&tty->write_wait, &wait); 2320 add_wait_queue(&tty->write_wait, &wait);
2326 while (1) { 2321 while (1) {
2327 set_current_state(TASK_INTERRUPTIBLE);
2328 if (signal_pending(current)) { 2322 if (signal_pending(current)) {
2329 retval = -ERESTARTSYS; 2323 retval = -ERESTARTSYS;
2330 break; 2324 break;
@@ -2378,12 +2372,11 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2378 } 2372 }
2379 up_read(&tty->termios_rwsem); 2373 up_read(&tty->termios_rwsem);
2380 2374
2381 schedule(); 2375 wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
2382 2376
2383 down_read(&tty->termios_rwsem); 2377 down_read(&tty->termios_rwsem);
2384 } 2378 }
2385break_out: 2379break_out:
2386 __set_current_state(TASK_RUNNING);
2387 remove_wait_queue(&tty->write_wait, &wait); 2380 remove_wait_queue(&tty->write_wait, &wait);
2388 if (b - buf != nr && tty->fasync) 2381 if (b - buf != nr && tty->fasync)
2389 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); 2382 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);