kernel/drivers/tty/sysrq.c, branch linux-6.9.y

/proc/sysrq-trigger: accept multiple keys at once

2023-11-25T07:23:16Z

This way we can do: `echo _reisub > /proc/sysrq-trigger` Instead of: `for i in r e i s u b; do echo "$i" > /proc/sysrq-trigger; done;` This can be very useful when trying to execute sysrq combo remotely or from userspace. When sending keys in multiple separate writes, userspace (eg. bash or ssh) can be killed before whole combo is completed. Therefore putting all keys in single write is more robust approach. Signed-off-by: Tomas Mudrunka Reviewed-by: Jiri Slaby Link: https://lore.kernel.org/r/20231120111451.527952-1-tomas.mudrunka@gmail.com Signed-off-by: Greg Kroah-Hartman

tty/sysrq: replace smp_processor_id() with get_cpu()

2023-10-10T06:52:24Z

The smp_processor_id() shouldn't be called from preemptible code. Instead use get_cpu() and put_cpu() which disables preemption in addition to getting the processor id. Enable preemption back after calling schedule_work() to make sure that the work gets scheduled on all cores other than the current core. We want to avoid a scenario where current core's stack trace is printed multiple times and one core's stack trace isn't printed because of scheduling of current task. This fixes the following bug: [ 119.143590] sysrq: Show backtrace of all active CPUs [ 119.143902] BUG: using smp_processor_id() in preemptible [00000000] code: bash/873 [ 119.144586] caller is debug_smp_processor_id+0x20/0x30 [ 119.144827] CPU: 6 PID: 873 Comm: bash Not tainted 5.10.124-dirty #3 [ 119.144861] Hardware name: QEMU QEMU Virtual Machine, BIOS 2023.05-1 07/22/2023 [ 119.145053] Call trace: [ 119.145093] dump_backtrace+0x0/0x1a0 [ 119.145122] show_stack+0x18/0x70 [ 119.145141] dump_stack+0xc4/0x11c [ 119.145159] check_preemption_disabled+0x100/0x110 [ 119.145175] debug_smp_processor_id+0x20/0x30 [ 119.145195] sysrq_handle_showallcpus+0x20/0xc0 [ 119.145211] __handle_sysrq+0x8c/0x1a0 [ 119.145227] write_sysrq_trigger+0x94/0x12c [ 119.145247] proc_reg_write+0xa8/0xe4 [ 119.145266] vfs_write+0xec/0x280 [ 119.145282] ksys_write+0x6c/0x100 [ 119.145298] __arm64_sys_write+0x20/0x30 [ 119.145315] el0_svc_common.constprop.0+0x78/0x1e4 [ 119.145332] do_el0_svc+0x24/0x8c [ 119.145348] el0_svc+0x10/0x20 [ 119.145364] el0_sync_handler+0x134/0x140 [ 119.145381] el0_sync+0x180/0x1c0 Cc: jirislaby@kernel.org Cc: stable@vger.kernel.org Fixes: 47cab6a722d4 ("debug lockups: Improve lockup detection, fix generic arch fallback") Signed-off-by: Muhammad Usama Anjum Link: https://lore.kernel.org/r/20231009162021.3607632-1-usama.anjum@collabora.com Signed-off-by: Greg Kroah-Hartman

Merge tag 'tty-6.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

2023-09-01T16:38:00Z

Pull tty/serial driver updates from Greg KH: "Here is the big set of tty and serial driver changes for 6.6-rc1. Lots of cleanups in here this cycle, and some driver updates. Short summary is: - Jiri's continued work to make the tty code and apis be a bit more sane with regards to modern kernel coding style and types - cpm_uart driver updates - n_gsm updates and fixes - meson driver updates - sc16is7xx driver updates - 8250 driver updates for different hardware types - qcom-geni driver fixes - tegra serial driver change - stm32 driver updates - synclink_gt driver cleanups - tty structure size reduction All of these have been in linux-next this week with no reported issues. The last bit of cleanups from Jiri and the tty structure size reduction came in last week, a bit late but as they were just style changes and size reductions, I figured they should get into this merge cycle so that others can work on top of them with no merge conflicts" * tag 'tty-6.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (199 commits) tty: shrink the size of struct tty_struct by 40 bytes tty: n_tty: deduplicate copy code in n_tty_receive_buf_real_raw() tty: n_tty: extract ECHO_OP processing to a separate function tty: n_tty: unify counts to size_t tty: n_tty: use u8 for chars and flags tty: n_tty: simplify chars_in_buffer() tty: n_tty: remove unsigned char casts from character constants tty: n_tty: move newline handling to a separate function tty: n_tty: move canon handling to a separate function tty: n_tty: use MASK() for masking out size bits tty: n_tty: make n_tty_data::num_overrun unsigned tty: n_tty: use time_is_before_jiffies() in n_tty_receive_overrun() tty: n_tty: use 'num' for writes' counts tty: n_tty: use output character directly tty: n_tty: make flow of n_tty_receive_buf_common() a bool Revert "tty: serial: meson: Add a earlycon for the T7 SoC" Documentation: devices.txt: Fix minors for ttyCPM* Documentation: devices.txt: Remove ttySIOC* Documentation: devices.txt: Remove ttyIOC* serial: 8250_bcm7271: improve bcm7271 8250 port ...

mm: remove arguments of show_mem()

2023-08-18T17:12:02Z

All callers of show_mem() pass 0 and NULL, so we can remove the two arguments by directly calling __show_mem(0, NULL, MAX_NR_ZONES - 1) in show_mem(). Link: https://lkml.kernel.org/r/20230630062253.189440-1-wangkefeng.wang@huawei.com Signed-off-by: Kefeng Wang Cc: Christophe Leroy Cc: Greg Kroah-Hartman Cc: Matthew Wilcox Cc: Michael Ellerman Cc: Nicholas Piggin Signed-off-by: Andrew Morton

tty: sysrq: use switch in sysrq_key_table_key2index()

2023-07-25T17:21:03Z

Using switch with range cases makes the code more aligned and readable. Expand also that 36 as explicit addition of 10 + 26 to make the source of the constant more obvious. Signed-off-by: Jiri Slaby (SUSE) Link: https://lore.kernel.org/r/20230712081811.29004-5-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: sysrq: switch the rest of keys to u8

2023-07-25T17:21:03Z

Propagate u8 more from the bottom to the interface, so that sysrq callers (usually drivers) see that u8 is expected. Signed-off-by: Jiri Slaby (SUSE) Link: https://lore.kernel.org/r/20230712081811.29004-4-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: sysrq: switch sysrq handlers from int to u8

2023-07-25T17:21:03Z

The passed parameter to sysrq handlers is a key (a character). So change the type from 'int' to 'u8'. Let it specifically be 'u8' for two reasons: * unsigned: unsigned values come from the upper layers (devices) and the tty layer assumes unsigned on most places, and * 8-bit: as that what's supposed to be one day in all the layers built on the top of tty. (Currently, we use mostly 'unsigned char' and somewhere still only 'char'. (But that also translates to the former thanks to -funsigned-char.)) Signed-off-by: Jiri Slaby (SUSE) Cc: Richard Henderson Cc: Ivan Kokshaysky Cc: Matt Turner Cc: Huacai Chen Cc: WANG Xuerui Cc: Thomas Bogendoerfer Cc: Michael Ellerman Cc: Nicholas Piggin Cc: Christophe Leroy Cc: "David S. Miller" Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Thomas Zimmermann Cc: David Airlie Cc: Daniel Vetter Cc: Jason Wessel Cc: Daniel Thompson Cc: Douglas Anderson Cc: "Rafael J. Wysocki" Cc: Len Brown Cc: Pavel Machek Cc: "Paul E. McKenney" Cc: Frederic Weisbecker Cc: Neeraj Upadhyay Cc: Joel Fernandes Cc: Josh Triplett Cc: Boqun Feng Cc: Steven Rostedt Cc: Mathieu Desnoyers Cc: Lai Jiangshan Cc: Zqiang Acked-by: Thomas Zimmermann # DRM Acked-by: WANG Xuerui # loongarch Acked-by: Paul E. McKenney Acked-by: Daniel Thompson Link: https://lore.kernel.org/r/20230712081811.29004-3-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: sysrq: rename and re-type i in sysrq_handle_loglevel()

2023-07-25T17:20:00Z

'i' is a too generic name for something which carries a 'loglevel'. Name it as such and make it 'u8', the same as key will become in the next patches. Note that we are not stripping any high bits away, 'key' is given only 8bit values. Signed-off-by: Jiri Slaby (SUSE) Link: https://lore.kernel.org/r/20230712081811.29004-2-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

treewide: Convert del_timer() to timer_shutdown()

2022-12-25T21:38:09Z

Due to several bugs caused by timers being re-armed after they are shutdown and just before they are freed, a new state of timers was added called "shutdown". After a timer is set to this state, then it can no longer be re-armed. The following script was run to find all the trivial locations where del_timer() or del_timer_sync() is called in the same function that the object holding the timer is freed. It also ignores any locations where the timer->function is modified between the del_timer*() and the free(), as that is not considered a "trivial" case. This was created by using a coccinelle script and the following commands: $ cat timer.cocci @@ expression ptr, slab; identifier timer, rfield; @@ ( - del_timer(&ptr->timer); + timer_shutdown(&ptr->timer); | - del_timer_sync(&ptr->timer); + timer_shutdown_sync(&ptr->timer); ) ... when strict when != ptr->timer ( kfree_rcu(ptr, rfield); | kmem_cache_free(slab, ptr); | kfree(ptr); ) $ spatch timer.cocci . > /tmp/t.patch $ patch -p1 < /tmp/t.patch Link: https://lore.kernel.org/lkml/20221123201306.823305113@linutronix.de/ Signed-off-by: Steven Rostedt (Google) Acked-by: Pavel Machek [ LED ] Acked-by: Kalle Valo [ wireless ] Acked-by: Paolo Abeni [ networking ] Signed-off-by: Linus Torvalds

Merge branch 'rework/kthreads' into for-linus

2022-06-23T17:11:28Z

kernel/drivers/tty/sysrq.c, branch linux-6.9.y

/proc/sysrq-trigger: accept multiple keys at once

tty/sysrq: replace smp_processor_id() with get_cpu()

Merge tag 'tty-6.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

mm: remove arguments of show_mem()

tty: sysrq: use switch in sysrq_key_table_key2index()

tty: sysrq: switch the rest of keys to u8

tty: sysrq: switch sysrq handlers from int to u8

tty: sysrq: rename and re-type i in sysrq_handle_loglevel()

treewide: Convert del_timer*() to timer_shutdown*()

Merge branch 'rework/kthreads' into for-linus

treewide: Convert del_timer() to timer_shutdown()