- 06 Nov, 2014 40 commits
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Sebastian Andrzej Siewior authored
if I boot with console=ttyS0 and the omap driver is module I end up with | console [ttyS0] disabled | omap8250 44e09000.serial: ttyS0 at MMIO 0x44e09000 (irq = 88, base_baud = 3000000) is a 8250 | Unable to handle kernel paging request at virtual address c07a9de0 | Modules linked in: 8250_omap(+) | CPU: 0 PID: 908 Comm: modprobe Not tainted 3.17.0-rc5+ #1593 | PC is at serial8250_console_setup+0x0/0xc8 | LR is at register_console+0x13c/0x3a4 | [<c0078788>] (register_console) from [<c02d0340>] (uart_add_one_port+0x3cc/0x420) | [<c02d0340>] (uart_add_one_port) from [<c02d38a4>] (serial8250_register_8250_port+0x298/0x39c) | [<c02d38a4>] (serial8250_register_8250_port) from [<bf006274>] (omap8250_probe+0x218/0x3dc [8250_omap]) | [<bf006274>] (omap8250_probe [8250_omap]) from [<c02e3424>] (platform_drv_probe+0x2c/0x5c) | [<c02e3424>] (platform_drv_probe) from [<c02e1eac>] (driver_probe_device+0x104/0x228) … | [<c009fa48>] (SyS_init_module) from [<c000e6e0>] (ret_fast_syscall+0x0/0x30) | Code: 7823603b f8314620 051b3013 491ed416 (44792204) because serial8250_console_setup() is already gone. Signed-off-by:
Sebastian Andrzej Siewior <bigeasy@linutronix.de> Reviewed-by:
Peter Hurley <peter@hurleysoftware.com> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Sebastian Andrzej Siewior authored
Frans reworded the two comments with better English for better understanding. His review hit the mailing list after the patch got applied so here is an incremental update. Reported-by:
Frans Klaver <frans.klaver@xsens.com> Signed-off-by:
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Janusz Uzycki authored
When using mxs-auart based console, sometime we need the sysrq function to help debugging kernel. The sysrq code is basically there, this patch just simply enable it. Signed-off-by:
Janusz Uzycki <j.uzycki@elproma.com.pl> Reviewed-by:
Fabio Estevam <fabio.estevam@freescale.com> Signed-off-by:
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Markus Pargmann authored
This error message is not necessary. The driver core code will print all probe error messages. It also resolves some error codes to proper error messages. For example -EPROBE_DEFER will only be printed as an info message. This patch removes the error message as the core prints the same information. Signed-off-by:
Markus Pargmann <mpa@pengutronix.de> Acked-by:
Felipe Balbi <balbi@ti.com> Signed-off-by:
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Peter Hurley authored
A port count mismatch occurs if mutex_lock_interruptible() exits uart_open() and the port has already been opened. This may prematurely close a port on an open tty. Since uart_close() is _always_ called if uart_open() fails, the port count must be corrected if errors occur. Always increment the port count in uart_open(), regardless of errors; always decrement the port count in uart_close(). Note that tty_port_close_start() decrements the port count when uart_open() was successful. Signed-off-by:
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Peter Hurley authored
uart_start() only claims the port->lock to call __uart_start(), which does the actual processing. Eliminate the extra acquire/release in uart_write(); call __uart_start() directly with port->lock already held. Signed-off-by:
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Peter Hurley authored
The key function of uart_add_one_port() is to cross-reference the UART driver's port structure with the serial core's state table; keep the assignments together and document this crucial association. Signed-off-by:
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Peter Hurley authored
tty_port_init() initializes close_delay and closing_wait to these same values; remove. Signed-off-by:
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Peter Hurley authored
The wrapped line looks wrong and out-of-place; leave it as >80 char line. Signed-off-by:
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Peter Hurley authored
Note the serial_struct flags for which the kernel ignores and performs no action. The flags cannot be removed since they form part of the userspace interface via the TIOCSSERIAL/TIOCGSERIAL ioctls. Signed-off-by:
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Peter Hurley authored
The userspace-defined ASYNC_* flags in include/uapi/linux/tty_flags.h are the authoritative bit definitions for the serial_struct flags, and thus for any derivative values or fields. Although the serial core provides the TIOCSSERIAL and TIOCGSERIAL ioctls to set and retrieve these flags from userspace, it defines these bits independently, as UPF_* macros. Define the UPF_* macros which are userspace-modifiable directly from the ASYNC_* symbolic constants. Add compile-time test to ensure the bits changeable by TIOCSSERIAL match the defined range in the uapi header. Add ASYNCB_MAGIC_MULTIPLIER to the uapi header since this bit is programmable by userspace. Signed-off-by:
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Peter Hurley authored
The low-level uart driver may modify termios settings to override settings that are not compatible with the uart, such as CRTSCTS. Thus, callers of the low-level uart driver's set_termios() method must hold termios_rwsem write lock to prevent concurrent access to termios, in case such override occurs. The termios_rwsem lock requirement does not extend to console setup (ie., uart_set_options), as console setup cannot race with tty operations. Nor does this lock requirement extend to functions which cannot be concurrent with tty ioctls (ie., uart_port_startup() and uart_resume_port()). Further, always claim the port mutex to protect hardware re-reprogramming in the set_termios() uart driver method. Note this is unnecessary for console initialization in uart_set_options() which cannot be concurrent with other uart operations. Signed-off-by:
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Peter Hurley authored
The tty buffers (and any line discipline buffers) must be flushed after the UART hardware has shutdown; otherwise, a racing open on the same tty may receive data from the previous session, which is a security hazard. However, holding the port mutex while flushing the line discipline buffers creates a lock inversion if the set_termios() handler takes the port mutex (as it does in the followup patch, 'serial: Fix locking for uart driver set_termios method'. Flush the ldisc buffers after dropping the port mutex; the tty lock is still held which prevents a concurrent open() from advancing while flushing. Since no new rx data is possible after uart_shutdown() until a new open reinitializes the port, the later flush has no impact on what data is being discarded. Signed-off-by:
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Peter Hurley authored
In the context of the final tty & port close, flushing the tx ring buffer after the hardware has already been shutdown and the ring buffer freed is neither required nor desirable. uart_flush_buffer() performs 3 operations: 1. Resets tx ring buffer indices, but the tx ring buffer has already been freed and the indices are reset if the port is re-opened. 2. Calls uart driver's flush_buffer() method 5 in-tree uart drivers define flush_buffer() methods: amba-pl011, atmel-serial, imx, serial-tegra, timbuart These have been refactored into the shutdown() method, if required. 3. Kicks the ldisc for more writing, but this is undesirable. The file handle is being released; any waiting writer will will be kicked out by tty_release() with a warning. Further, the N_TTY ldisc may generate SIGIO for a file handle which is no longer valid. Cc: Nicolas Ferre <nicolas.ferre@atmel.com> Cc: Russell King <linux@arm.linux.org.uk> Cc: Laxman Dewangan <ldewangan@nvidia.com> Signed-off-by: -
Peter Hurley authored
tty_ldisc_flush() first clears the line discipline input buffer, then clears the tty flip buffers. However, this allows for existing data in the tty flip buffers to be added after the ldisc input buffer has been cleared, but before the flip buffers have been cleared. Add an optional ldisc parameter to tty_buffer_flush() to allow tty_ldisc_flush() to pass the ldisc to clear. NB: Initially, the plan was to do this automatically in tty_buffer_flush(). However, an audit of the behavior of existing line disciplines showed that performing a ldisc buffer flush on ioctl(TCFLSH) was not always the outcome. For example, some line disciplines have flush_buffer() methods but not ioctl() methods, so a ->flush_buffer() command would be unexpected. Reviewed-by:
Alan Cox <alan@linux.intel.com> Signed-off-by:
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Peter Hurley authored
When changing the ldisc on one end of a pty pair, there may be waiting readers/writers on the other end which may not exit from the ldisc i/o loop, preventing tty_ldisc_lock_pair_timeout() from acquiring the other side's ldisc lock. Only acquire this side's ldisc lock; although this will no longer prevent the other side from writing new input, that input will not be processed until after the ldisc change completes. This has no effect on normal ttys; new input from the driver was never disabled. Remove tty_ldisc_enable_pair(). Reviewed-by:
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Peter Hurley authored
When hanging up one end of a pty pair, there may be waiting readers/writers on the other end which may not exit, preventing tty_ldisc_lock_pair() from acquiring the other side's ldisc lock. Only acquire this side's ldisc lock; although this will no longer prevent the other side from writing new input, that input will not be processing until after the ldisc hangup is complete. Reported-by:
Sasha Levin <sasha.levin@oracle.com> Reviewed-by:
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Peter Hurley authored
tty_ldisc_lock(), tty_ldisc_unlock(), and tty_ldisc_lock_nested() are low-level aliases for the underlying lock mechanism. Rename with double underscore to allow for new, higher level functions with those names. Reviewed-by:
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Peter Hurley authored
When releasing one end of a pty pair, that end may just have written to the other, which the input processing worker, flush_to_ldisc(), is still working on but has not completed the copy to the other end's read buffer. So input may not appear to be available to a waiting reader but yet TTY_OTHER_CLOSED is now observed. The n_tty line discipline has worked around this by waiting for input processing to complete and then re-checking if input is available before exiting with -EIO. Since the tty/ldisc lock reordering, the wait for input processing to complete can now occur during final close before setting TTY_OTHER_CLOSED. In this way, a waiting reader is guaranteed to see input available (if any) before observing TTY_OTHER_CLOSED. Reviewed-by:
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Peter Hurley authored
With the revised tty lock order and lockdep annotation, claiming the pty slave lock is now safe while still holding the pty master lock. Signed-off-by:
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Peter Hurley authored
The tty_unhangup() function is not defined. Reviewed-by:
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Peter Hurley authored
Eliminate the requirement of specifying the tty lock nesting at lock time; instead, set the lock subclass for slave ptys at pty install (normal ttys and master ptys use subclass 0). Signed-off-by:
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Peter Hurley authored
When releasing the master pty, the slave pty also needs to be locked to prevent concurrent tty count changes for the slave pty and to ensure that only one parallel master and slave release observe the final close, and proceed to destruct the pty pair. Conversely, when releasing the slave pty, locking the master pty is not necessary (since the master's state can be inferred by the slave tty count). Introduce tty_lock_slave()/tty_unlock_slave() which acquires/releases the tty lock of the slave pty. Remove tty_lock_pair()/tty_unlock_pair(). Dropping the tty_lock is no longer required to re-establish a stable lock order. Reviewed-by:
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Peter Hurley authored
The local o_tty variable in tty_release() is now accessed only when closing the pty master. Set o_tty to slave pty when closing pty master, otherwise NULL; use o_tty != NULL as replacement for pty_master. Reviewed-by:
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Peter Hurley authored
Passing the 'other' tty to tty_release_checks() only makes sense for a pty pair; make o_tty scope local instead. Reviewed-by:
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Peter Hurley authored
Passing the 'other' tty to tty_ldisc_release() only makes sense for a pty pair; make o_tty function local instead. Reviewed-by:
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Peter Hurley authored
Perform work flush for both ends of a pty pair within tty_flush_works(), rather than calling twice. Reviewed-by:
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Peter Hurley authored
When the slave side closes and its tty count is 0, the pty pair can be destroyed; the master side must have already closed for the slave side tty count to be 0. Thus, only the pty master close must check if the slave side has closed by checking the slave tty count. Remove the pre-computed closing flags and check the actual count(s). Regular ttys are unaffected by this change. Reviewed-by:
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Peter Hurley authored
Holding the tty_lock() is necessary to prevent concurrent changes to the tty count that may cause it to differ from the open file list count. The tty_lock() is already held at all call sites. NB: Note that the check for the pty master tty count is safe because the slave's tty_lock() is held while decrementing the pty master tty count. Reviewed-by:
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Peter Hurley authored
Releasing the tty locks while waiting for the tty wait queues to be empty is no longer necessary nor desirable. Prior to "tty: Don't take tty_mutex for tty count changes", dropping the tty locks was necessary to reestablish the correct lock order between tty_mutex and the tty locks. Dropping the global tty_mutex was necessary; otherwise new ttys could not have been opened while waiting. However, without needing the global tty_mutex held, the tty locks for the releasing tty can now be held through the sleep. The sanity check is for abnormal conditions caused by kernel bugs, not for recoverable errors caused by misbehaving userspace; dropping the tty locks only allows the tty state to get more sideways. Reviewed-by:
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Peter Hurley authored
Holding tty_mutex is no longer required to serialize changes to the tty_count or to prevent concurrent opens of closing ttys; tty_lock() is sufficient. Reviewed-by:
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Peter Hurley authored
Now that re-open is not permitted for a legacy BSD pty master, using TTY_CLOSING to indicate when a tty can be torn-down is no longer necessary. Reviewed-by:
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Peter Hurley authored
Holding tty_mutex for a tty re-open is no longer necessary since "tty: Clarify re-open behavior of master ptys". Because the slave tty count is no longer accessed by tty_reopen(), holding tty_mutex to prevent concurrent final tty_release() of the slave pty is not required. As with "tty: Re-open /dev/tty without tty_mutex", holding a tty kref until the tty_lock is acquired is sufficient to ensure the tty has not been freed, which, in turn, is sufficient to ensure the tty_lock can be safely acquired and the tty count can be safely retrieved. A non-zero tty count with the tty lock held guarantees that release_tty() has not run and cannot run concurrently with tty_reopen(). Change tty_driver_lookup_tty() to acquire the tty kref, which allows the tty_mutex to be dropped before acquiring the tty lock. Dropping the tty_mutex before attempting the tty_lock allows other ttys to be opened and released, without needing this tty_reopen() to complete. Reviewed-by:
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Peter Hurley authored
Opening /dev/tty (ie., the controlling tty for the current task) is always a re-open of the underlying tty. Because holding the tty_lock is sufficient for safely re-opening a tty, and because having a tty kref is sufficient for safely acquiring the tty_lock [1], tty_open_current_tty() does not require holding tty_mutex. Repurpose tty_open_current_tty() to perform the re-open itself and refactor tty_open(). [1] Analysis of safely re-opening the current tty w/o tty_mutex get_current_tty() gets a tty kref from the already kref'ed tty value of current->signal->tty while holding the sighand lock for the current task. This guarantees that the tty pointer returned from get_current_tty() points to a tty which remains referenceable while holding the kref. Although release_tty() may run concurrently, and thus the driver reference may be removed, release_one_tty() cannot have run, and won't while holding the tty kref. This, in turn, guarantees the tty_lock() can safely be acquired (since tty->magic and tty->legacy_mutex are still a valid dereferences). The tty_lock() also gets a tty kref to prevent the tty_unlock() from dereferencing a released tty. Thus, the kref returned from get_current_tty() can be released. Lastly, the first operation of tty_reopen() is to check the tty count. If non-zero, this ensures release_tty() is not running concurrently, and the driver references have not been removed. Reviewed-by:
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Peter Hurley authored
Opening the slave BSD pty first already returns -EIO from the slave pty_open(), which in turn causes the newly installed tty pair to be released before returning from tty_open(). However, this can also cause a parallel master BSD pty open to fail because the pty pair destruction may already been taking place in tty_release(). Failing at driver->install() if the slave pty is opened first ensures that a pty master open cannot fail, because the driver tables will not have been updated so tty_driver_lookup_tty() won't find the master pty (and attempt to "re-open" it). In turn, this guarantees that any tty with a tty->count == 0 is in final close (rather than never opened). Reviewed-by:
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Peter Hurley authored
Although perhaps not obvious, the TTY_CLOSING bit is set when the tty count has been decremented to 0 (which occurs while holding tty_lock). The only other case when tty count is 0 during a re-open is when a legacy BSD pty master has been opened in parallel but after the pty slave, which is unsupported and returns an error. Thus !tty->count contains the complete set of degenerate conditions under which a tty open fails. Reviewed-by:
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Peter Hurley authored
Re-opening master ptys is not allowed. Once opened and for the remaining lifetime of the master pty, its tty count is 1. If its tty count has dropped to 0, then the master pty was closed and TTY_CLOSING was set, and destruction may begin imminently. Besides the normal case of a legacy BSD pty master being re-opened (which always returns -EIO), this code is only reachable in 2 degenerate cases: 1. The pty master is the controlling terminal (this is possible through the TIOCSCTTY ioctl). pty masters are not designed to be controlling terminals and it's an oversight that tiocsctty() ever let that happen. The attempted open of /dev/tty will always fail. No known program does this. 2. The legacy BSD pty slave was opened first. The slave open will fail in pty_open() and tty_release() will commence. But before tty_release() claims the tty_mutex, there is a very small window where a parallel master open might succeed. In a test of racing legacy BSD slave and master parallel opens, where: slave open attempts: 10000 success:4527 failure:5473 master open attempts: 11728 success:5789 failure:5939 only 8 master open attempts would have succeeded reaching this code and successfully opened the master pty. This case is not possible with SysV ptys. Always return -EIO if a master pty is re-opened or the slave is opened first and the master opened in parallel (for legacy BSD ptys). Furthermore, now that changing the slave's count is not required, the tty_lock is sufficient for preventing concurrent changes to the tty being re-opened (or failing re-opening). Reviewed-by: -
Peter Hurley authored
Now that tty_ldisc_hangup() does not drop the tty lock, it is no longer possible to observe TTY_HUPPING while holding the tty lock on another cpu. Remove TTY_HUPPING bit definition. Reviewed-by:
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Peter Hurley authored
Dropping the tty lock to acquire the tty->ldisc_sem allows several race conditions (such as hangup while changing the ldisc) which requires extra states and testing. The ldisc_sem->tty_lock lock order has not been required since tty buffer ownership was moved to tty_port. Reviewed-by:
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Peter Hurley authored
The tty->ldisc_sem write lock is sufficient for serializing changes to tty->ldisc; holding the tty lock is not required. Reviewed-by:
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