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path: root/drivers/tty/tty_ldisc.c
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* tty: Revert the tty locking series, it needs more workLinus Torvalds2012-06-021-38/+29
| | | | | | | | | | | | | | | | | | | | | | This reverts the tty layer change to use per-tty locking, because it's not correct yet, and fixing it will require some more deep surgery. The main revert is d29f3ef39be4 ("tty_lock: Localise the lock"), but there are several smaller commits that built upon it, they also get reverted here. The list of reverted commits is: fde86d310886 - tty: add lockdep annotations 8f6576ad476b - tty: fix ldisc lock inversion trace d3ca8b64b97e - pty: Fix lock inversion b1d679afd766 - tty: drop the pty lock during hangup abcefe5fc357 - tty/amiserial: Add missing argument for tty_unlock() fd11b42e3598 - cris: fix missing tty arg in wait_event_interruptible_tty call d29f3ef39be4 - tty_lock: Localise the lock The revert had a trivial conflict in the 68360serial.c staging driver that got removed in the meantime. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* tty: fix ldisc lock inversion traceAlan Cox2012-05-291-16/+25
| | | | | | | | | | | | | This is caused by tty_release using tty_lock_pair to lock both sides of the pty/tty pair, and then tty_ldisc_release dropping and relocking one side only. We can drop both fine, so drop both to avoid any lock ordering concerns. Rework the release path to fix the new locking model. Signed-off-by: Alan Cox <alan@linux.intel.com> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* tty: move global ldisc idle waitqueue to the individual ldiscIvo Sieben2012-05-101-3/+4
| | | | | | | | | | | The global wait_queue that is used for line discipline idle handling is moved to a separate wait_queue for each line instance. This prevents unnecessary blocking on one line, because of idle handling on another line. Signed-off-by: Ivo Sieben <meltedpianoman@gmail.com> Acked-by: Alan Cox <alan@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty_lock: Localise the lockAlan Cox2012-05-041-15/+15
| | | | | | | | | | | | In each remaining case the tty_lock is associated with a specific tty. This means we can now lock on a per tty basis. We do need tty_lock_pair() for the pty case. Uglier but still a step in the right direction. [fixed up calls in 3 missing drivers - gregkh] Signed-off-by: Alan Cox <alan@linux.intel.com> Acked-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* Merge 3.2-rc3 into tty-next to handle merge conflict in tty_ldisc.cGreg Kroah-Hartman2011-11-261-7/+23
|\ | | | | | | Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| * TTY: ldisc, wait for ldisc infinitely in hangupJiri Slaby2011-11-171-2/+17
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | For /dev/console case, we do not kill all ldisc users. It's due to redirected_tty_write test in __tty_hangup. In that case there still might be a process waiting e.g. in n_tty_read for input. We wait for such processes to disappear. The problem is that we use a timeout. After this timeout, we continue closing the ldisc and start freeing tty resources. It obviously leads to crashes when the other process is woken. So to fix this, we wait infinitely before reiniting the ldisc. (The tiocsetd remains untouched -- times out after 5s.) This is nicely reproducible with this run from shell: exec 0<>/dev/console 1<>/dev/console 2<>/dev/console and stopping a getty like: systemctl stop serial-getty@ttyS0.service The crash proper may be produced only under load or with constified timing the same as for 92f6fa09b. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Cc: Dave Young <hidave.darkstar@gmail.com> Cc: Dave Jones <davej@redhat.com> Cc: Ben Hutchings <ben@decadent.org.uk> Cc: Dmitriy Matrosov <sgf.dma@gmail.com> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| * TTY: ldisc, move wait idle to callerJiri Slaby2011-11-171-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | It is the only place where reinit is called from. And we really need to wait for the old ldisc to go once. Actually this is the place where the waiting originally was (before removed and re-added later). This will make the fix in the following patch easier to implement. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Cc: Dave Young <hidave.darkstar@gmail.com> Cc: Dave Jones <davej@redhat.com> Cc: Ben Hutchings <ben@decadent.org.uk> Cc: Dmitriy Matrosov <sgf.dma@gmail.com> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| * TTY: ldisc, allow waiting for ldisc arbitrarily longJiri Slaby2011-11-171-5/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | To fix a nasty bug in ldisc hup vs. reinit we need to wait infinitely long for ldisc to be gone. So here we add a parameter to tty_ldisc_wait_idle to allow that. This is only a preparation for the real fix which is done in the following patches. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Cc: Dave Young <hidave.darkstar@gmail.com> Cc: Dave Jones <davej@redhat.com> Cc: Ben Hutchings <ben@decadent.org.uk> Cc: Dmitriy Matrosov <sgf.dma@gmail.com> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
* | TTY: ldisc, remove some unneeded includesJiri Slaby2011-11-171-19/+1
| | | | | | | | | | | | | | | | | | They were cut&pasted from tty_io. Many of them are not needed in tty_ldisc. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Cc: Alan Cox <alan@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
* | tty_ldisc: remove unnecessary negative return check for wait_event_timeoutDave Young2011-11-151-2/+0
|/ | | | | | | | | wait_event_timeout always return value >= 0 remove the unnecessary ret < 0 check Signed-off-by: Dave Young <dyoung@redhat.com> Acked-by: Jiri Slaby <jslaby@suse.cz> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
* TTY: remove tty_lockedJiri Slaby2011-08-231-1/+0
| | | | | | | | | | | | We used it really only serial and ami_serial. The rest of the callsites were BUG/WARN_ONs to check if BTM is held. Now that we pruned tty_locked from both of the real users, we can get rid of tty_lock along with __big_tty_mutex_owner. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Acked-by: Arnd Bergmann <arnd@arndb.de> Cc: Alan Cox <alan@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
* TTY: ldisc, do not close until there are readersJiri Slaby2011-06-071-1/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | We restored tty_ldisc_wait_idle in 100eeae2c5c (TTY: restore tty_ldisc_wait_idle). We used it in the ldisc changing path to fix the case where there are tasks in n_tty_read waiting for data and somebody tries to change ldisc. Similar to the case above, there may be also tasks waiting in n_tty_read while hangup is performed. As 65b770468e98 (tty-ldisc: turn ldisc user count into a proper refcount) removed the wait-until-idle from all paths, hangup path won't wait for them to disappear either now. So add it back even to the hangup path. There is a difference, we need uninterruptible sleep as there is obviously HUP signal pending. So tty_ldisc_wait_idle now sleeps without possibility to be interrupted. This is what original tty_ldisc_wait_idle did. After the wait idle reintroduction (100eeae2c5c), we have had interruptible sleeps for the ldisc changing path. But as there is a 5s timeout anyway, we don't allow it to be interrupted from now on. It's not worth the added complexity of deciding what kind of sleep we want. Before 65b770468e98 tty_ldisc_release was called also from tty_ldisc_release. It is called from tty_release, so I don't think we need to restore that one. This is nicely reproducible after constifying the timing when drivers/tty/n_tty.c is patched as follows ("TTY: ntty, add one more sanity check" patch is needed to actually see it explode): %% -1548,6 +1549,7 @@ static int n_tty_open(struct tty_struct *tty) /* These are ugly. Currently a malloc failure here can panic */ if (!tty->read_buf) { + msleep(100); tty->read_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL); if (!tty->read_buf) return -ENOMEM; %% -1785,6 +1788,7 @@ do_it_again: break; } timeout = schedule_timeout(timeout); + msleep(20); continue; } __set_current_state(TASK_RUNNING); ===== With a process: ===== while (1) { int fd = open(argv[1], O_RDWR); read(fd, buf, sizeof(buf)); close(fd); } ===== and its child: ===== setsid(); while (1) { int fd = open(tty, O_RDWR|O_NOCTTY); ioctl(fd, TIOCSCTTY, 1); vhangup(); close(fd); usleep(100 * (10 + random() % 1000)); } ===== EOF ===== References: https://bugzilla.novell.com/show_bug.cgi?id=693374 References: https://bugzilla.novell.com/show_bug.cgi?id=694509 Signed-off-by: Jiri Slaby <jslaby@suse.cz> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: stable <stable@kernel.org> [32, 33, 34, 39] Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
* TTY: introduce deinit helpers for proper ldisc shutdownJiri Slaby2011-04-191-0/+13
| | | | | | | | | | | | | | | | Introduce deinitialize_tty_struct which should be called after initialize_tty_struct and before successfull tty_ldisc_setup. It calls tty_ldisc_deinit which is opposite of tty_ldisc_init. It only puts a reference to ldisc and assigns NULL to tty->ldisc. It will be used to shut down ldisc when tty_release cannot be called yet. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: Julian Anastasov <ja@ssi.bg> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
* tty: stop using "delayed_work" in the tty layerLinus Torvalds2011-03-221-7/+7
| | | | | | | | | | | | | | | | | | | | | | | Using delayed-work for tty flip buffers ends up causing us to wait for the next tick to complete some actions. That's usually not all that noticeable, but for certain latency-critical workloads it ends up being totally unacceptable. As an extreme case of this, passing a token back-and-forth over a pty will take two ticks per iteration, so even just a thousand iterations will take 8 seconds assuming a common 250Hz configuration. Avoiding the whole delayed work issue brings that ping-pong test-case down to 0.009s on my machine. In more practical terms, this latency has been a performance problem for things like dive computer simulators (simulating the serial interface using the ptys) and for other environments (Alan mentions a CP/M emulator). Reported-by: Jef Driesen <jefdriesen@telenet.be> Acked-by: Greg KH <gregkh@suse.de> Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Merge branch 'config' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/bklLinus Torvalds2011-03-161-2/+0
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | * 'config' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/bkl: BKL: That's all, folks fs/locks.c: Remove stale FIXME left over from BKL conversion ipx: remove the BKL appletalk: remove the BKL x25: remove the BKL ufs: remove the BKL hpfs: remove the BKL drivers: remove extraneous includes of smp_lock.h tracing: don't trace the BKL adfs: remove the big kernel lock
| * drivers: remove extraneous includes of smp_lock.hArnd Bergmann2011-03-021-2/+0
| | | | | | | | | | | | | | | | These were missed the last time I cleaned this up globally, because of code moving around or new code getting merged. Signed-off-by: Arnd Bergmann <arnd@arndb.de>
* | tty_ldisc: don't use flush_scheduled_work()Tejun Heo2011-02-031-2/+15
|/ | | | | | | | | | flush_scheduled_work() is scheduled to be deprecated. Explicitly sync flush the used work items instead. Note that before this change, flush_scheduled_work() wouldn't have properly flushed tty->buf.work if it were on timer. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
* TTY: ldisc, fix open flag handlingJiri Slaby2010-11-291-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | When a concrete ldisc open fails in tty_ldisc_open, we forget to clear TTY_LDISC_OPEN. This causes a false warning on the next ldisc open: WARNING: at drivers/char/tty_ldisc.c:445 tty_ldisc_open+0x26/0x38() Hardware name: System Product Name Modules linked in: ... Pid: 5251, comm: a.out Tainted: G W 2.6.32-5-686 #1 Call Trace: [<c1030321>] ? warn_slowpath_common+0x5e/0x8a [<c1030357>] ? warn_slowpath_null+0xa/0xc [<c119311c>] ? tty_ldisc_open+0x26/0x38 [<c11936c5>] ? tty_set_ldisc+0x218/0x304 ... So clear the bit when failing... Introduced in c65c9bc3efa (tty: rewrite the ldisc locking) back in 2.6.31-rc1. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Cc: Alan Cox <alan@linux.intel.com> Reported-by: Sergey Lapin <slapin@ossfans.org> Tested-by: Sergey Lapin <slapin@ossfans.org> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
* tty_ldisc: Fix BUG() on hangupPhilippe Rétornaz2010-11-091-7/+13
| | | | | | | | | | | | | | A kernel BUG when bluetooth rfcomm connection drop while the associated serial port is open is sometime triggered. It seems that the line discipline can disappear between the tty_ldisc_put and tty_ldisc_get. This patch fall back to the N_TTY line discipline if the previous discipline is not available anymore. Signed-off-by: Philippe Retornaz <philippe.retornaz@epfl.ch> Acked-by: Alan Cox <alan@linux.intel.com> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
* TTY: restore tty_ldisc_wait_idleJiri Slaby2010-11-091-0/+29
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | It was removed in 65b770468e98 (tty-ldisc: turn ldisc user count into a proper refcount), but we need to wait for last user to quit the ldisc before we close it in tty_set_ldisc. Otherwise weird things start to happen. There might be processes waiting in tty_read->n_tty_read on tty->read_wait for input to appear and at that moment, a change of ldisc is fatal. n_tty_close is called, it frees read_buf and the waiting process is still in the middle of reading and goes nuts after it is woken. Previously we prevented close to happen when others are in ldisc ops by tty_ldisc_wait_idle in tty_set_ldisc. But the commit above removed that. So revoke the change and test whether there is 1 user (=we), and allow the close then. We can do that without ldisc/tty locks, because nobody else can open the device due to TTY_LDISC_CHANGING bit set, so we in fact wait for everybody to leave. I don't understand why tty_ldisc_lock would be needed either when the counter is an atomic variable, so this is a lockless tty_ldisc_wait_idle. On the other hand, if we fail to wait (timeout or signal), we have to reenable the halted ldiscs, so we take ldisc lock and reuse the setup path at the end of tty_set_ldisc. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Tested-by: Sebastian Andrzej Siewior <bigeasy@breakpoint.cc> LKML-Reference: <20101031104136.GA511@Chamillionaire.breakpoint.cc> LKML-Reference: <1287669539-22644-1-git-send-email-jslaby@suse.cz> Cc: Alan Cox <alan@linux.intel.com> Cc: stable@kernel.org [32, 33, 36] Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
* TTY: create drivers/tty and move the tty core files thereGreg Kroah-Hartman2010-11-051-0/+915
The tty code should be in its own subdirectory and not in the char driver with all of the cruft that is currently there. Based on work done by Arnd Bergmann <arnd@arndb.de> Acked-by: Arnd Bergmann <arnd@arndb.de> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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