Messages in this thread Patch in this message | | | From | John Ogness <> | Subject | [PATCH printk v5 39/40] printk: relieve console_lock of list synchronization duties | Date | Wed, 16 Nov 2022 17:27:51 +0106 |
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The console_list_lock provides synchronization for console list and console->flags updates. All call sites that were using the console_lock for this synchronization have either switched to use the console_list_lock or the SRCU list iterator.
Remove console_lock usage for console list updates and console->flags updates.
Signed-off-by: John Ogness <john.ogness@linutronix.de> --- kernel/printk/printk.c | 44 +++++++++++++++++++----------------------- 1 file changed, 20 insertions(+), 24 deletions(-)
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index ece34abbc9cc..094017c4a5ca 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -86,8 +86,8 @@ EXPORT_SYMBOL(oops_in_progress); static DEFINE_MUTEX(console_mutex); /* - * console_sem protects console_list and console->flags updates, and also - * provides serialization for access to the entire console driver system. + * console_sem protects updates to console->seq and console_suspended, + * and also provides serialization for console printing. */ static DEFINE_SEMAPHORE(console_sem); HLIST_HEAD(console_list); @@ -2639,10 +2639,10 @@ static int console_cpu_notify(unsigned int cpu) } /** - * console_lock - lock the console system for exclusive use. + * console_lock - block the console subsystem from printing * - * Acquires a lock which guarantees that the caller has - * exclusive access to the console system and console_list. + * Acquires a lock which guarantees that no consoles will + * be in or enter their write() callback. * * Can sleep, returns nothing. */ @@ -2659,10 +2659,10 @@ void console_lock(void) EXPORT_SYMBOL(console_lock); /** - * console_trylock - try to lock the console system for exclusive use. + * console_trylock - try to block the console subsystem from printing * - * Try to acquire a lock which guarantees that the caller has exclusive - * access to the console system and console_list. + * Try to acquire a lock which guarantees that no consoles will + * be in or enter their write() callback. * * returns 1 on success, and 0 on failure to acquire the lock. */ @@ -2919,10 +2919,10 @@ static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handove } /** - * console_unlock - unlock the console system + * console_unlock - unblock the console subsystem from printing * - * Releases the console_lock which the caller holds on the console system - * and the console driver list. + * Releases the console_lock which the caller holds to block printing of + * the console subsystem. * * While the console_lock was held, console output may have been buffered * by printk(). If this is the case, console_unlock(); emits @@ -3109,9 +3109,7 @@ void console_stop(struct console *console) { __pr_flush(console, 1000, true); console_list_lock(); - console_lock(); console_srcu_write_flags(console, console->flags & ~CON_ENABLED); - console_unlock(); console_list_unlock(); /* @@ -3127,9 +3125,7 @@ EXPORT_SYMBOL(console_stop); void console_start(struct console *console) { console_list_lock(); - console_lock(); console_srcu_write_flags(console, console->flags | CON_ENABLED); - console_unlock(); console_list_unlock(); __pr_flush(console, 1000, true); } @@ -3246,6 +3242,12 @@ static void console_init_seq(struct console *newcon, bool bootcon_registered) * the furthest behind. */ if (bootcon_registered && !keep_bootcon) { + /* + * Hold the console_lock to stop console printing and + * guarantee safe access to console->seq. + */ + console_lock(); + /* * Flush all consoles and set the console to start at * the next unprinted sequence number. @@ -3272,6 +3274,8 @@ static void console_init_seq(struct console *newcon, bool bootcon_registered) } } } + + console_unlock(); } } } @@ -3370,7 +3374,6 @@ void register_console(struct console *newcon) } newcon->dropped = 0; - console_lock(); console_init_seq(newcon, bootcon_registered); /* @@ -3390,7 +3393,6 @@ void register_console(struct console *newcon) } else { hlist_add_behind_rcu(&newcon->node, console_list.first); } - console_unlock(); /* * No need to synchronize SRCU here! The caller does not rely @@ -3438,15 +3440,11 @@ static int unregister_console_locked(struct console *console) if (res > 0) return 0; - console_lock(); - /* Disable it unconditionally */ console_srcu_write_flags(console, console->flags & ~CON_ENABLED); - if (!console_is_registered_locked(console)) { - console_unlock(); + if (!console_is_registered_locked(console)) return -ENODEV; - } hlist_del_init_rcu(&console->node); @@ -3462,8 +3460,6 @@ static int unregister_console_locked(struct console *console) if (!hlist_empty(&console_list) && console->flags & CON_CONSDEV) console_srcu_write_flags(console_first(), console_first()->flags | CON_CONSDEV); - console_unlock(); - /* * Ensure that all SRCU list walks have completed. All contexts * must not be able to see this console in the list so that any -- 2.30.2
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