From: John Ogness <[email protected]> [ Upstream commit 26873e3e7f0cb26c45e6ad63656f9fe36b2aa31b ]
Allowing irq_work to be scheduled while trying to suspend has shown to cause problems as some architectures interpret the pending interrupts as a reason to not suspend. This became a problem for printk() with the introduction of NBCON consoles. With every printk() call, NBCON console printing kthreads are woken by queueing irq_work. This means that irq_work continues to be queued due to printk() calls late in the suspend procedure. Avoid this problem by preventing printk() from queueing irq_work once console suspending has begun. This applies to triggering NBCON and legacy deferred printing as well as klogd waiters. Since triggering of NBCON threaded printing relies on irq_work, the pr_flush() within console_suspend_all() is used to perform the final flushing before suspending consoles and blocking irq_work queueing. NBCON consoles that are not suspended (due to the usage of the "no_console_suspend" boot argument) transition to atomic flushing. Introduce a new global variable @console_irqwork_blocked to flag when irq_work queueing is to be avoided. The flag is used by printk_get_console_flush_type() to avoid allowing deferred printing and switch NBCON consoles to atomic flushing. It is also used by vprintk_emit() to avoid klogd waking. Add WARN_ON_ONCE(console_irqwork_blocked) to the irq_work queuing functions to catch any code that attempts to queue printk irq_work during the suspending/resuming procedure. Cc: [email protected] # 6.13.x because no drivers in 6.12.x Fixes: 6b93bb41f6ea ("printk: Add non-BKL (nbcon) console basic infrastructure") Closes: https://lore.kernel.org/lkml/db9pr04mb8429e7ddf2d93c2695de401d92...@db9pr04mb8429.eurprd04.prod.outlook.com Signed-off-by: John Ogness <[email protected]> Reviewed-by: Petr Mladek <[email protected]> Tested-by: Sherry Sun <[email protected]> Link: https://patch.msgid.link/[email protected] Signed-off-by: Petr Mladek <[email protected]> --- kernel/printk/internal.h | 8 +++--- kernel/printk/nbcon.c | 7 +++++ kernel/printk/printk.c | 58 +++++++++++++++++++++++++++++----------- 3 files changed, 55 insertions(+), 18 deletions(-) diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h index 5eef70000b43..08b7d933263c 100644 --- a/kernel/printk/internal.h +++ b/kernel/printk/internal.h @@ -225,6 +225,8 @@ struct console_flush_type { bool legacy_offload; }; +extern bool console_irqwork_blocked; + /* * Identify which console flushing methods should be used in the context of * the caller. @@ -236,7 +238,7 @@ static inline void printk_get_console_flush_type(struct console_flush_type *ft) switch (nbcon_get_default_prio()) { case NBCON_PRIO_NORMAL: if (have_nbcon_console && !have_boot_console) { - if (printk_kthreads_running) + if (printk_kthreads_running && !console_irqwork_blocked) ft->nbcon_offload = true; else ft->nbcon_atomic = true; @@ -246,7 +248,7 @@ static inline void printk_get_console_flush_type(struct console_flush_type *ft) if (have_legacy_console || have_boot_console) { if (!is_printk_legacy_deferred()) ft->legacy_direct = true; - else + else if (!console_irqwork_blocked) ft->legacy_offload = true; } break; @@ -259,7 +261,7 @@ static inline void printk_get_console_flush_type(struct console_flush_type *ft) if (have_legacy_console || have_boot_console) { if (!is_printk_legacy_deferred()) ft->legacy_direct = true; - else + else if (!console_irqwork_blocked) ft->legacy_offload = true; } break; diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c index 4d23305689e9..36113d2f9d5a 100644 --- a/kernel/printk/nbcon.c +++ b/kernel/printk/nbcon.c @@ -1276,6 +1276,13 @@ void nbcon_kthreads_wake(void) if (!printk_kthreads_running) return; + /* + * It is not allowed to call this function when console irq_work + * is blocked. + */ + if (WARN_ON_ONCE(console_irqwork_blocked)) + return; + cookie = console_srcu_read_lock(); for_each_console_srcu(con) { if (!(console_srcu_read_flags(con) & CON_NBCON)) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 178d4b46736c..9d46876b8817 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -489,6 +489,9 @@ bool have_boot_console; /* See printk_legacy_allow_panic_sync() for details. */ bool legacy_allow_panic_sync; +/* Avoid using irq_work when suspending. */ +bool console_irqwork_blocked; + #ifdef CONFIG_PRINTK DECLARE_WAIT_QUEUE_HEAD(log_wait); static DECLARE_WAIT_QUEUE_HEAD(legacy_wait); @@ -2410,7 +2413,7 @@ asmlinkage int vprintk_emit(int facility, int level, if (ft.legacy_offload) defer_console_output(); - else + else if (!console_irqwork_blocked) wake_up_klogd(); return printed_len; @@ -2714,10 +2717,20 @@ void suspend_console(void) { struct console *con; + if (console_suspend_enabled) + pr_info("Suspending console(s) (use no_console_suspend to debug)\n"); + + /* + * Flush any console backlog and then avoid queueing irq_work until + * console_resume_all(). Until then deferred printing is no longer + * triggered, NBCON consoles transition to atomic flushing, and + * any klogd waiters are not triggered. + */ + pr_flush(1000, true); + console_irqwork_blocked = true; + if (!console_suspend_enabled) return; - pr_info("Suspending console(s) (use no_console_suspend to debug)\n"); - pr_flush(1000, true); console_list_lock(); for_each_console(con) @@ -2738,26 +2751,34 @@ void resume_console(void) struct console_flush_type ft; struct console *con; - if (!console_suspend_enabled) - return; - - console_list_lock(); - for_each_console(con) - console_srcu_write_flags(con, con->flags & ~CON_SUSPENDED); - console_list_unlock(); - /* - * Ensure that all SRCU list walks have completed. All printing - * contexts must be able to see they are no longer suspended so - * that they are guaranteed to wake up and resume printing. + * Allow queueing irq_work. After restoring console state, deferred + * printing and any klogd waiters need to be triggered in case there + * is now a console backlog. */ - synchronize_srcu(&console_srcu); + console_irqwork_blocked = false; + + if (console_suspend_enabled) { + console_list_lock(); + for_each_console(con) + console_srcu_write_flags(con, con->flags & ~CON_SUSPENDED); + console_list_unlock(); + + /* + * Ensure that all SRCU list walks have completed. All printing + * contexts must be able to see they are no longer suspended so + * that they are guaranteed to wake up and resume printing. + */ + synchronize_srcu(&console_srcu); + } printk_get_console_flush_type(&ft); if (ft.nbcon_offload) nbcon_kthreads_wake(); if (ft.legacy_offload) defer_console_output(); + else + wake_up_klogd(); pr_flush(1000, true); } @@ -4483,6 +4504,13 @@ static void __wake_up_klogd(int val) if (!printk_percpu_data_ready()) return; + /* + * It is not allowed to call this function when console irq_work + * is blocked. + */ + if (WARN_ON_ONCE(console_irqwork_blocked)) + return; + preempt_disable(); /* * Guarantee any new records can be seen by tasks preparing to wait -- 2.49.1
-=-=-=-=-=-=-=-=-=-=-=- Links: You receive all messages sent to this group. View/Reply Online (#16262): https://lists.yoctoproject.org/g/linux-yocto/message/16262 Mute This Topic: https://lists.yoctoproject.org/mt/117611994/21656 Group Owner: [email protected] Unsubscribe: https://lists.yoctoproject.org/g/linux-yocto/unsub [[email protected]] -=-=-=-=-=-=-=-=-=-=-=-
