Messages in this thread Patch in this message | | | From | John Ogness <> | Subject | [PATCH printk v1 18/18] printk: Perform atomic flush in console_flush_on_panic() | Date | Thu, 2 Mar 2023 21:02:18 +0106 |
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Typically the panic() function will take care of atomic flushing the non-BKL consoles on panic. However, there are several users of console_flush_on_panic() outside of panic().
Also perform atomic flushing in console_flush_on_panic(). A new function cons_force_seq() is implemented to support the mode=CONSOLE_REPLAY_ALL feature.
Signed-off-by: John Ogness <john.ogness@linutronix.de> --- kernel/printk/internal.h | 2 ++ kernel/printk/printk.c | 28 ++++++++++++++++++++++------ kernel/printk/printk_nobkl.c | 24 ++++++++++++++++++++++++ 3 files changed, 48 insertions(+), 6 deletions(-)
diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h index a417e3992b7a..f147ca386afa 100644 --- a/kernel/printk/internal.h +++ b/kernel/printk/internal.h @@ -79,6 +79,7 @@ bool cons_nobkl_init(struct console *con); bool cons_alloc_percpu_data(struct console *con); void cons_kthread_create(struct console *con); void cons_wake_threads(void); +void cons_force_seq(struct console *con, u64 seq); /* * Check if the given console is currently capable and allowed to print @@ -148,6 +149,7 @@ static inline void cons_kthread_create(struct console *con) { } static inline bool printk_percpu_data_ready(void) { return false; } static inline bool cons_nobkl_init(struct console *con) { return true; } static inline void cons_nobkl_cleanup(struct console *con) { } +static inline void cons_force_seq(struct console *con, u64 seq) { } #endif /* CONFIG_PRINTK */ diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 015c240f9f04..9a8ba8b3dca5 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3160,6 +3160,28 @@ void console_unblank(void) */ void console_flush_on_panic(enum con_flush_mode mode) { + struct console *c; + short flags; + int cookie; + u64 seq; + + seq = prb_first_valid_seq(prb); + + /* + * Safely flush the atomic consoles before trying to flush any + * BKL/legacy consoles. + */ + if (mode == CONSOLE_REPLAY_ALL) { + cookie = console_srcu_read_lock(); + for_each_console_srcu(c) { + flags = console_srcu_read_flags(c); + if (flags & CON_NO_BKL) + cons_force_seq(c, seq); + } + console_srcu_read_unlock(cookie); + } + cons_atomic_flush(NULL, true); + if (!have_bkl_console) return; @@ -3174,12 +3196,6 @@ void console_flush_on_panic(enum con_flush_mode mode) console_may_schedule = 0; if (mode == CONSOLE_REPLAY_ALL) { - struct console *c; - int cookie; - u64 seq; - - seq = prb_first_valid_seq(prb); - cookie = console_srcu_read_lock(); for_each_console_srcu(c) { /* diff --git a/kernel/printk/printk_nobkl.c b/kernel/printk/printk_nobkl.c index 53989c8f1dbc..ac2ba785500e 100644 --- a/kernel/printk/printk_nobkl.c +++ b/kernel/printk/printk_nobkl.c @@ -233,6 +233,30 @@ static void cons_seq_init(struct console *con) #endif } +/** + * cons_force_seq - Force a specified sequence number for a console + * @con: Console to work on + * @seq: Sequence number to force + * + * This function is only intended to be used in emergency situations. In + * particular: console_flush_on_panic(CONSOLE_REPLAY_ALL) + */ +void cons_force_seq(struct console *con, u64 seq) +{ +#ifdef CONFIG_64BIT + struct cons_state old; + struct cons_state new; + + do { + cons_state_read(con, CON_STATE_CUR, &old); + copy_bit_state(new, old); + new.seq = seq; + } while (!cons_state_try_cmpxchg(con, CON_STATE_CUR, &old, &new)); +#else + atomic_set(&ACCESS_PRIVATE(con, atomic_seq), seq); +#endif +} + static inline u64 cons_expand_seq(u64 seq) { u64 rbseq; -- 2.30.2
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