kernel.git/kernel/printk/printk.c, branch linux-6.7.y

printk: Update @console_may_schedule in console_trylock_spinning()

2024-04-03T13:11:43Z

[ Upstream commit 8076972468584d4a21dab9aa50e388b3ea9ad8c7 ] console_trylock_spinning() may takeover the console lock from a schedulable context. Update @console_may_schedule to make sure it reflects a trylock acquire. Reported-by: Mukesh Ojha Closes: https://lore.kernel.org/lkml/20240222090538.23017-1-quic_mojha@quicinc.com Fixes: dbdda842fe96 ("printk: Add console owner and waiter logic to load balance console writes") Signed-off-by: John Ogness Reviewed-by: Mukesh Ojha Reviewed-by: Petr Mladek Link: https://lore.kernel.org/r/875xybmo2z.fsf@jogness.linutronix.de Signed-off-by: Petr Mladek Signed-off-by: Sasha Levin

serial: Lock console when calling into driver before registration

2024-04-03T13:11:17Z

[ Upstream commit 801410b26a0e8b8a16f7915b2b55c9528b69ca87 ] During the handoff from earlycon to the real console driver, we have two separate drivers operating on the same device concurrently. In the case of the 8250 driver these concurrent accesses cause problems due to the driver's use of banked registers, controlled by LCR.DLAB. It is possible for the setup(), config_port(), pm() and set_mctrl() callbacks to set DLAB, which can cause the earlycon code that intends to access TX to instead access DLL, leading to missed output and corruption on the serial line due to unintended modifications to the baud rate. In particular, for setup() we have: univ8250_console_setup() -> serial8250_console_setup() -> uart_set_options() -> serial8250_set_termios() -> serial8250_do_set_termios() -> serial8250_do_set_divisor() For config_port() we have: serial8250_config_port() -> autoconfig() For pm() we have: serial8250_pm() -> serial8250_do_pm() -> serial8250_set_sleep() For set_mctrl() we have (for some devices): serial8250_set_mctrl() -> omap8250_set_mctrl() -> __omap8250_set_mctrl() To avoid such problems, let's make it so that the console is locked during pre-registration calls to these callbacks, which will prevent the earlycon driver from running concurrently. Remove the partial solution to this problem in the 8250 driver that locked the console only during autoconfig_irq(), as this would result in a deadlock with the new approach. The console continues to be locked during autoconfig_irq() because it can only be called through uart_configure_port(). Although this patch introduces more locking than strictly necessary (and in particular it also locks during the call to rs485_config() which is not affected by this issue as far as I can tell), it follows the principle that it is the responsibility of the generic console code to manage the earlycon handoff by ensuring that earlycon and real console driver code cannot run concurrently, and not the individual drivers. Signed-off-by: Peter Collingbourne Reviewed-by: John Ogness Link: https://linux-review.googlesource.com/id/I7cf8124dcebf8618e6b2ee543fa5b25532de55d8 Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20240304214350.501253-1-pcc@google.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

printk: Disable passing console lock owner completely during panic()

2024-03-26T22:18:11Z

[ Upstream commit d04d5882cd678b898a9d7c5aee6afbe9e6e77fcd ] The commit d51507098ff91 ("printk: disable optimistic spin during panic") added checks to avoid becoming a console waiter if a panic is in progress. However, the transition to panic can occur while there is already a waiter. The current owner should not pass the lock to the waiter because it might get stopped or blocked anytime. Also the panic context might pass the console lock owner to an already stopped waiter by mistake. It might happen when console_flush_on_panic() ignores the current lock owner, for example: CPU0 CPU1 ---- ---- console_lock_spinning_enable() console_trylock_spinning() [CPU1 now console waiter] NMI: panic() panic_other_cpus_shutdown() [stopped as console waiter] console_flush_on_panic() console_lock_spinning_enable() [print 1 record] console_lock_spinning_disable_and_check() [handover to stopped CPU1] This results in panic() not flushing the panic messages. Fix these problems by disabling all spinning operations completely during panic(). Another advantage is that it prevents possible deadlocks caused by "console_owner_lock". The panic() context does not need to take it any longer. The lockless checks are safe because the functions become NOPs when they see the panic in progress. All operations manipulating the state are still synchronized by the lock even when non-panic CPUs would notice the panic synchronously. The current owner might stay spinning. But non-panic() CPUs would get stopped anyway and the panic context will never start spinning. Fixes: dbdda842fe96 ("printk: Add console owner and waiter logic to load balance console writes") Signed-off-by: John Ogness Link: https://lore.kernel.org/r/20240207134103.1357162-12-john.ogness@linutronix.de Signed-off-by: Petr Mladek Signed-off-by: Sasha Levin

printk: Add this_cpu_in_panic()

2024-03-26T22:18:10Z

[ Upstream commit 36652d0f3bf34899e82d31a5fa9e2bdd02fd6381 ] There is already panic_in_progress() and other_cpu_in_panic(), but checking if the current CPU is the panic CPU must still be open coded. Add this_cpu_in_panic() to complete the set. Signed-off-by: John Ogness Reviewed-by: Petr Mladek Link: https://lore.kernel.org/r/20240207134103.1357162-8-john.ogness@linutronix.de Signed-off-by: Petr Mladek Stable-dep-of: b1c4c67a5e90 ("printk: ringbuffer: Skip non-finalized records in panic") Signed-off-by: Sasha Levin

printk: Wait for all reserved records with pr_flush()

2024-03-26T22:18:10Z

[ Upstream commit ac7d7844c64d15603daa3e905a311ddcfbb4bc91 ] Currently pr_flush() will only wait for records that were available to readers at the time of the call (using prb_next_seq()). But there may be more records (non-finalized) that have following finalized records. pr_flush() should wait for these to print as well. Particularly because any trailing finalized records may be the messages that the calling context wants to ensure are printed. Add a new ringbuffer function prb_next_reserve_seq() to return the sequence number following the most recently reserved record. This guarantees that pr_flush() will wait until all current printk() messages (completed or in progress) have been printed. Fixes: 3b604ca81202 ("printk: add pr_flush()") Signed-off-by: John Ogness Reviewed-by: Petr Mladek Link: https://lore.kernel.org/r/20240207134103.1357162-10-john.ogness@linutronix.de Signed-off-by: Petr Mladek Signed-off-by: Sasha Levin

Merge tag 'tty-6.7-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

2023-11-04T01:44:25Z

Pull tty and serial updates from Greg KH: "Here is the big set of tty/serial driver changes for 6.7-rc1. Included in here are: - console/vgacon cleanups and removals from Arnd - tty core and n_tty cleanups from Jiri - lots of 8250 driver updates and cleanups - sc16is7xx serial driver updates - dt binding updates - first set of port lock wrapers from Thomas for the printk fixes coming in future releases - other small serial and tty core cleanups and updates All of these have been in linux-next for a while with no reported issues" * tag 'tty-6.7-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (193 commits) serdev: Replace custom code with device_match_acpi_handle() serdev: Simplify devm_serdev_device_open() function serdev: Make use of device_set_node() tty: n_gsm: add copyright Siemens Mobility GmbH tty: n_gsm: fix race condition in status line change on dead connections serial: core: Fix runtime PM handling for pending tx vgacon: fix mips/sibyte build regression dt-bindings: serial: drop unsupported samsung bindings tty: serial: samsung: drop earlycon support for unsupported platforms tty: 8250: Add note for PX-835 tty: 8250: Fix IS-200 PCI ID comment tty: 8250: Add Brainboxes Oxford Semiconductor-based quirks tty: 8250: Add support for Intashield IX cards tty: 8250: Add support for additional Brainboxes PX cards tty: 8250: Fix up PX-803/PX-857 tty: 8250: Fix port count of PX-257 tty: 8250: Add support for Intashield IS-100 tty: 8250: Add support for Brainboxes UP cards tty: 8250: Add support for additional Brainboxes UC cards tty: 8250: Remove UC-257 and UC-431 ...

Merge branch 'rework/nbcon-base' into for-linus

2023-11-02T12:04:59Z

Merge branch 'rework/misc-cleanups' into for-linus

2023-11-02T12:00:34Z

Merge branch 'for-6.7' into for-linus

2023-11-02T12:00:20Z

printk: printk: Remove unnecessary statements＇len = 0;＇

2023-10-24T08:19:48Z

In the following two functions, len has already been assigned a value of 0 when defining the variable, so remove 'len=0;'. Signed-off-by: Li kunyu Reviewed-by: Petr Mladek Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20231023062359.130633-1-kunyu@nfschina.com