linux/kernel/printk, branch v6.14

treewide: const qualify ctl_tables where applicable

2025-01-28T12:48:37Z

Add the const qualifier to all the ctl_tables in the tree except for watchdog_hardlockup_sysctl, memory_allocation_profiling_sysctls, loadpin_sysctl_table and the ones calling register_net_sysctl (./net, drivers/inifiniband dirs). These are special cases as they use a registration function with a non-const qualified ctl_table argument or modify the arrays before passing them on to the registration function. Constifying ctl_table structs will prevent the modification of proc_handler function pointers as the arrays would reside in .rodata. This is made possible after commit 78eb4ea25cd5 ("sysctl: treewide: constify the ctl_table argument of proc_handlers") constified all the proc_handlers. Created this by running an spatch followed by a sed command: Spatch: virtual patch @ depends on !(file in "net") disable optional_qualifier @ identifier table_name != { watchdog_hardlockup_sysctl, iwcm_ctl_table, ucma_ctl_table, memory_allocation_profiling_sysctls, loadpin_sysctl_table }; @@ + const struct ctl_table table_name [] = { ... }; sed: sed --in-place \ -e "s/struct ctl_table .table = &uts_kern/const struct ctl_table *table = \&uts_kern/" \ kernel/utsname_sysctl.c Reviewed-by: Song Liu Acked-by: Steven Rostedt (Google) # for kernel/trace/ Reviewed-by: Martin K. Petersen # SCSI Reviewed-by: Darrick J. Wong # xfs Acked-by: Jani Nikula Acked-by: Corey Minyard Acked-by: Wei Liu Acked-by: Thomas Gleixner Reviewed-by: Bill O'Donnell Acked-by: Baoquan He Acked-by: Ashutosh Dixit Acked-by: Anna Schumaker Signed-off-by: Joel Granados

Merge branch 'for-6.14-cpu_sync-fixup' into for-linus

2025-01-20T12:40:52Z

printk: Defer legacy printing when holding printk_cpu_sync

2024-12-16T12:26:31Z

The documentation of printk_cpu_sync_get() clearly states that the owner must never perform any activities where it waits for a CPU. For legacy printing there can be spinning on the console_lock and on the port lock. Therefore legacy printing must be deferred when holding the printk_cpu_sync. Note that in the case of emergency states, atomic consoles are not prevented from printing when printk is deferred. This is appropriate because they do not spin-wait indefinitely for other CPUs. Reported-by: Rik van Riel Closes: https://lore.kernel.org/r/20240715232052.73eb7fb1@imladris.surriel.com Signed-off-by: John Ogness Fixes: 55d6af1d6688 ("lib/nmi_backtrace: explicitly serialize banner and regs") Reviewed-by: Petr Mladek Link: https://lore.kernel.org/r/20241209111746.192559-3-john.ogness@linutronix.de Signed-off-by: Petr Mladek

printk: Remove redundant deferred check in vprintk()

2024-12-16T12:26:09Z

The helper printk_get_console_flush_type() is already calling is_printk_legacy_deferred() to determine if legacy printing is to be offloaded. Therefore there is no need for vprintk() to perform this check as well. Remove the redundant check from vprintk(). Signed-off-by: John Ogness Reviewed-by: Petr Mladek Link: https://lore.kernel.org/r/20241209111746.192559-2-john.ogness@linutronix.de Signed-off-by: Petr Mladek

printk: Fix signed integer overflow when defining LOG_BUF_LEN_MAX

2024-12-12T09:10:03Z

Shifting 1 << 31 on a 32-bit int causes signed integer overflow, which leads to undefined behavior. To prevent this, cast 1 to u32 before performing the shift, ensuring well-defined behavior. This change explicitly avoids any potential overflow by ensuring that the shift occurs on an unsigned 32-bit integer. Signed-off-by: Kuan-Wei Chiu Acked-by: Petr Mladek Link: https://lore.kernel.org/r/20240928113608.1438087-1-visitorckw@gmail.com Signed-off-by: Petr Mladek

Merge tag 'printk-for-6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

2024-11-20T17:21:11Z

Pull printk updates from Petr Mladek: - Print more precise information about the printk log buffer memory usage. - Make sure that the sysrq title is shown on the console even when deferred. - Do not enable earlycon by `console=` which is meant to disable the default console. * tag 'printk-for-6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux: printk: add dummy printk_force_console_enter/exit helpers tty: sysrq: Use printk_force_console context on __handle_sysrq printk: Introduce FORCE_CON flag printk: Improve memory usage logging during boot init: Don't proxy `console=` to earlycon

Merge branch 'for-6.13-force-console' into for-linus

2024-11-18T13:07:05Z

printk: Introduce FORCE_CON flag

2024-11-11T11:53:31Z

Introduce FORCE_CON flag to printk. The new flag will make it possible to create a context where printk messages will never be suppressed. This mechanism will be used in the next patch to create a force_con context on sysrq handling, removing an existing workaround on the loglevel global variable. The workaround existed to make sure that sysrq header messages were sent to all consoles, but this doesn't work with deferred messages because the loglevel might be restored to its original value before a console flushes the messages. Signed-off-by: Marcos Paulo de Souza Reviewed-by: John Ogness Reviewed-by: Petr Mladek Acked-by: Greg Kroah-Hartman Link: https://lore.kernel.org/r/20241105-printk-loud-con-v2-1-bd3ecdf7b0e4@suse.com Signed-off-by: Petr Mladek

seqlock, treewide: Switch to non-raw seqcount_latch interface

2024-11-05T11:55:35Z

Switch all instrumentable users of the seqcount_latch interface over to the non-raw interface. Co-developed-by: "Peter Zijlstra (Intel)" Signed-off-by: "Peter Zijlstra (Intel)" Signed-off-by: Marco Elver Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20241104161910.780003-5-elver@google.com

printk: Improve memory usage logging during boot

2024-10-16T09:36:19Z

When the initial printk ring buffer size is updated, setup_log_buf() allocates a new ring buffer, as well as a set of meta-data structures for the new ring buffer. The function also emits the new size of the ring buffer, but not the size of the meta-data structures. This makes it difficult to assess how changing the log buffer size impacts memory usage during boot. For instance, increasing the ring buffer size from 512 KB to 1 MB through the command line yields an increase of 2304 KB in reserved memory at boot, while the only obvious change is the 512 KB difference in the ring buffer sizes: log_buf_len=512K: printk: log_buf_len: 524288 bytes Memory: ... (... 733252K reserved ...) log_buf_len=1M: printk: log_buf_len: 1048576 bytes Memory: ... (... 735556K reserved ...) This is because of how the size of the meta-data structures scale with the size of the ring buffer. Even when there aren't changes to the printk ring buffer size (i.e. the initial size == 1 << CONFIG_LOG_BUF_SHIFT), it is impossible to tell how much memory is consumed by the printk ring buffer during boot. Therefore, unconditionally log the sizes of the printk ring buffer and its meta-data structures, so that it's easier to understand how changing the log buffer size (either through the command line or by changing CONFIG_LOG_BUF_SHIFT) affects boot time memory usage. With the new logs, it is much easier to see exactly why the memory increased by 2304 KB: log_buf_len=512K: printk: log buffer data + meta data: 524288 + 1835008 = 2359296 bytes Memory: ... (... 733252K reserved ...) log_buf_len=1M: printk: log buffer data + meta data: 1048576 + 3670016 = 4718592 bytes Memory: ... (... 735556K reserved ...) Signed-off-by: Isaac J. Manjarres Reviewed-by: Petr Mladek Tested-by: Petr Mladek Link: https://lore.kernel.org/r/20240930184826.3595221-1-isaacmanjarres@google.com [pmladek@suse.com: Updated the examples in the commit message, simplified comment for default buffer.] Signed-off-by: Petr Mladek