From 37b164578826406a173ca7c20d9ba7430134d23e Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Thu, 16 Oct 2014 13:51:30 -0400 Subject: tty: Fix high cpu load if tty is unreleaseable Kernel oops can cause the tty to be unreleaseable (for example, if n_tty_read() crashes while on the read_wait queue). This will cause tty_release() to endlessly loop without sleeping. Use a killable sleep timeout which grows by 2n+1 jiffies over the interval [0, 120 secs.) and then jumps to forever (but still killable). NB: killable just allows for the task to be rewoken manually, not to be terminated. Cc: # since before 2.6.32 Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_io.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'drivers/tty/tty_io.c') diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 16a2c0237dd6..4021c10d9908 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1709,6 +1709,7 @@ int tty_release(struct inode *inode, struct file *filp) int pty_master, tty_closing, o_tty_closing, do_sleep; int idx; char buf[64]; + long timeout = 0; if (tty_paranoia_check(tty, inode, __func__)) return 0; @@ -1793,7 +1794,11 @@ int tty_release(struct inode *inode, struct file *filp) __func__, tty_name(tty, buf)); tty_unlock_pair(tty, o_tty); mutex_unlock(&tty_mutex); - schedule(); + schedule_timeout_killable(timeout); + if (timeout < 120 * HZ) + timeout = 2 * timeout + 1; + else + timeout = MAX_SCHEDULE_TIMEOUT; } /* -- cgit v1.2.3 From 494c1eac7e73f719af9d474a96ec8494c33efd6a Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Thu, 16 Oct 2014 13:54:36 -0400 Subject: tty: Prevent "read/write wait queue active!" log flooding Only print one warning when a task is on the read_wait or write_wait wait queue at final tty release. Cc: # 3.4.x+ Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_io.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'drivers/tty/tty_io.c') diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 4021c10d9908..0508a1d8e4cd 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1710,6 +1710,7 @@ int tty_release(struct inode *inode, struct file *filp) int idx; char buf[64]; long timeout = 0; + int once = 1; if (tty_paranoia_check(tty, inode, __func__)) return 0; @@ -1790,8 +1791,11 @@ int tty_release(struct inode *inode, struct file *filp) if (!do_sleep) break; - printk(KERN_WARNING "%s: %s: read/write wait queue active!\n", - __func__, tty_name(tty, buf)); + if (once) { + once = 0; + printk(KERN_WARNING "%s: %s: read/write wait queue active!\n", + __func__, tty_name(tty, buf)); + } tty_unlock_pair(tty, o_tty); mutex_unlock(&tty_mutex); schedule_timeout_killable(timeout); -- cgit v1.2.3