/* Number of registered extended console drivers. */
static int nr_ext_console_drivers;
-/*
- * Used to synchronize printing kthreads against direct printing via
- * console_trylock/console_unlock.
- *
- * Values:
- * -1 = console kthreads atomically blocked (via global trylock)
- * 0 = no kthread printing, console not locked (via trylock)
- * >0 = kthread(s) actively printing
- *
- * Note: For synchronizing against direct printing via
- * console_lock/console_unlock, see the @lock variable in
- * struct console.
- */
-static atomic_t console_kthreads_active = ATOMIC_INIT(0);
-
-#define console_kthreads_atomic_tryblock() \
- (atomic_cmpxchg(&console_kthreads_active, 0, -1) == 0)
-#define console_kthreads_atomic_unblock() \
- atomic_cmpxchg(&console_kthreads_active, -1, 0)
-#define console_kthreads_atomically_blocked() \
- (atomic_read(&console_kthreads_active) == -1)
-
-#define console_kthread_printing_tryenter() \
- atomic_inc_unless_negative(&console_kthreads_active)
-#define console_kthread_printing_exit() \
- atomic_dec(&console_kthreads_active)
-
/*
* Helper macros to handle lockdep when locking/unlocking console_sem. We use
* macros instead of functions so that _RET_IP_ contains useful information.
return unlikely(atomic_read(&panic_cpu) != PANIC_CPU_INVALID);
}
-/*
- * Tracks whether kthread printers are all blocked. A value of true implies
- * that the console is locked via console_lock() or the console is suspended.
- * Writing to this variable requires holding @console_sem.
- */
-static bool console_kthreads_blocked;
-
-/*
- * Block all kthread printers from a schedulable context.
- *
- * Requires holding @console_sem.
- */
-static void console_kthreads_block(void)
-{
- struct console *con;
-
- for_each_console(con) {
- mutex_lock(&con->lock);
- con->blocked = true;
- mutex_unlock(&con->lock);
- }
-
- console_kthreads_blocked = true;
-}
-
-/*
- * Unblock all kthread printers from a schedulable context.
- *
- * Requires holding @console_sem.
- */
-static void console_kthreads_unblock(void)
-{
- struct console *con;
-
- for_each_console(con) {
- mutex_lock(&con->lock);
- con->blocked = false;
- mutex_unlock(&con->lock);
- }
-
- console_kthreads_blocked = false;
-}
-
/*
* This is used for debugging the mess that is the VT code by
* keeping track if we have the console semaphore held. It's
down_console_sem();
console_suspended = 0;
console_unlock();
+
+ /*
+ * While suspended, new records may have been added to the
+ * ringbuffer. Wake up the kthread printers to print them.
+ */
+ wake_up_klogd();
+
pr_flush(1000, true);
}
/* If trylock fails, someone else is doing the printing */
if (console_trylock())
console_unlock();
- else {
- /*
- * If a new CPU comes online, the conditions for
- * printer_should_wake() may have changed for some
- * kthread printer with !CON_ANYTIME.
- */
- wake_up_klogd();
- }
+
+ /* Wake kthread printers. Some may have become usable. */
+ wake_up_klogd();
}
return 0;
}
down_console_sem();
if (console_suspended)
return;
- console_kthreads_block();
console_locked = 1;
console_may_schedule = 1;
}
up_console_sem();
return 0;
}
- if (!console_kthreads_atomic_tryblock()) {
- up_console_sem();
- return 0;
- }
console_locked = 1;
console_may_schedule = 0;
return 1;
int is_console_locked(void)
{
- return (console_locked || atomic_read(&console_kthreads_active));
+ return console_locked;
}
EXPORT_SYMBOL(is_console_locked);
* Check if the given console is currently capable and allowed to print
* records.
*
- * Requires holding the console_lock.
+ * Requires the console_lock.
*/
static inline bool console_is_usable(struct console *con)
{
static void __console_unlock(void)
{
console_locked = 0;
-
- /*
- * Depending on whether console_lock() or console_trylock() was used,
- * appropriately allow the kthread printers to continue.
- */
- if (console_kthreads_blocked)
- console_kthreads_unblock();
- else
- console_kthreads_atomic_unblock();
-
- /*
- * New records may have arrived while the console was locked.
- * Wake the kthread printers to print them.
- */
- wake_up_klogd();
-
up_console_sem();
}
*
* @handover will be set to true if a printk waiter has taken over the
* console_lock, in which case the caller is no longer holding the
- * console_lock. Otherwise it is set to false. A NULL pointer may be provided
- * to disable allowing the console_lock to be taken over by a printk waiter.
+ * console_lock. Otherwise it is set to false.
*
* Returns false if the given console has no next record to print, otherwise
* true.
*
- * Requires the console_lock if @handover is non-NULL.
- * Requires con->lock otherwise.
+ * Requires the console_lock.
*/
-static bool __console_emit_next_record(struct console *con, char *text, char *ext_text,
- char *dropped_text, bool *handover)
+static bool console_emit_next_record(struct console *con, char *text, char *ext_text,
+ char *dropped_text, bool *handover)
{
- static atomic_t panic_console_dropped = ATOMIC_INIT(0);
+ static int panic_console_dropped;
struct printk_info info;
struct printk_record r;
unsigned long flags;
prb_rec_init_rd(&r, &info, text, CONSOLE_LOG_MAX);
- if (handover)
- *handover = false;
+ *handover = false;
if (!prb_read_valid(prb, con->seq, &r))
return false;
if (con->seq != r.info->seq) {
con->dropped += r.info->seq - con->seq;
con->seq = r.info->seq;
- if (panic_in_progress() &&
- atomic_fetch_inc_relaxed(&panic_console_dropped) > 10) {
+ if (panic_in_progress() && panic_console_dropped++ > 10) {
suppress_panic_printk = 1;
pr_warn_once("Too many dropped messages. Suppress messages on non-panic CPUs to prevent livelock.\n");
}
len = record_print_text(&r, console_msg_format & MSG_FORMAT_SYSLOG, printk_time);
}
- if (handover) {
- /*
- * While actively printing out messages, if another printk()
- * were to occur on another CPU, it may wait for this one to
- * finish. This task can not be preempted if there is a
- * waiter waiting to take over.
- *
- * Interrupts are disabled because the hand over to a waiter
- * must not be interrupted until the hand over is completed
- * (@console_waiter is cleared).
- */
- printk_safe_enter_irqsave(flags);
- console_lock_spinning_enable();
-
- /* don't trace irqsoff print latency */
- stop_critical_timings();
- }
+ /*
+ * While actively printing out messages, if another printk()
+ * were to occur on another CPU, it may wait for this one to
+ * finish. This task can not be preempted if there is a
+ * waiter waiting to take over.
+ *
+ * Interrupts are disabled because the hand over to a waiter
+ * must not be interrupted until the hand over is completed
+ * (@console_waiter is cleared).
+ */
+ printk_safe_enter_irqsave(flags);
+ console_lock_spinning_enable();
+ stop_critical_timings(); /* don't trace print latency */
call_console_driver(con, write_text, len, dropped_text);
+ start_critical_timings();
con->seq++;
- if (handover) {
- start_critical_timings();
- *handover = console_lock_spinning_disable_and_check();
- printk_safe_exit_irqrestore(flags);
- }
+ *handover = console_lock_spinning_disable_and_check();
+ printk_safe_exit_irqrestore(flags);
skip:
return true;
}
-/*
- * Print a record for a given console, but allow another printk() caller to
- * take over the console_lock and continue printing.
- *
- * Requires the console_lock, but depending on @handover after the call, the
- * caller may no longer have the console_lock.
- *
- * See __console_emit_next_record() for argument and return details.
- */
-static bool console_emit_next_record_transferable(struct console *con, char *text, char *ext_text,
- char *dropped_text, bool *handover)
-{
- /*
- * Handovers are only supported if threaded printers are atomically
- * blocked. The context taking over the console_lock may be atomic.
- */
- if (!console_kthreads_atomically_blocked()) {
- *handover = false;
- handover = NULL;
- }
-
- return __console_emit_next_record(con, text, ext_text, dropped_text, handover);
-}
-
/*
* Print out all remaining records to all consoles.
*
if (con->flags & CON_EXTENDED) {
/* Extended consoles do not print "dropped messages". */
- progress = console_emit_next_record_transferable(con, &text[0],
- &ext_text[0], NULL, handover);
+ progress = console_emit_next_record(con, &text[0],
+ &ext_text[0], NULL,
+ handover);
} else {
- progress = console_emit_next_record_transferable(con, &text[0],
- NULL, &dropped_text[0], handover);
+ progress = console_emit_next_record(con, &text[0],
+ NULL, &dropped_text[0],
+ handover);
}
if (*handover)
return false;
if (oops_in_progress) {
if (down_trylock_console_sem() != 0)
return;
- if (!console_kthreads_atomic_tryblock()) {
- up_console_sem();
- return;
- }
} else
console_lock();
console_lock();
console->flags |= CON_ENABLED;
console_unlock();
+
+ /* Wake the newly enabled kthread printer. */
+ wake_up_klogd();
+
__pr_flush(console, 1000, true);
}
EXPORT_SYMBOL(console_start);
newcon->dropped = 0;
newcon->thread = NULL;
- newcon->blocked = true;
- mutex_init(&newcon->lock);
if (newcon->flags & CON_PRINTBUFFER) {
/* Get a consistent copy of @syslog_seq. */
console_unlock();
}
-/*
- * Print a record for a given console, not allowing another printk() caller
- * to take over. This is appropriate for contexts that do not have the
- * console_lock.
- *
- * See __console_emit_next_record() for argument and return details.
- */
-static bool console_emit_next_record(struct console *con, char *text, char *ext_text,
- char *dropped_text)
-{
- return __console_emit_next_record(con, text, ext_text, dropped_text, NULL);
-}
-
static bool printer_should_wake(struct console *con, u64 seq)
{
short flags;
if (kthread_should_stop() || !printk_kthreads_available)
return true;
- if (con->blocked ||
- console_kthreads_atomically_blocked()) {
+ if (console_suspended)
return false;
- }
/*
* This is an unsafe read from con->flags, but a false positive is
struct console *con = data;
char *dropped_text = NULL;
char *ext_text = NULL;
+ bool handover;
u64 seq = 0;
char *text;
int error;
if (error)
continue;
- error = mutex_lock_interruptible(&con->lock);
- if (error)
- continue;
+ console_lock();
- if (con->blocked ||
- !console_kthread_printing_tryenter()) {
- /* Another context has locked the console_lock. */
- mutex_unlock(&con->lock);
+ if (console_suspended) {
+ up_console_sem();
continue;
}
- /*
- * Although this context has not locked the console_lock, it
- * is known that the console_lock is not locked and it is not
- * possible for any other context to lock the console_lock.
- * Therefore it is safe to read con->flags.
- */
-
- if (!__console_is_usable(con->flags)) {
- console_kthread_printing_exit();
- mutex_unlock(&con->lock);
+ if (!console_is_usable(con)) {
+ __console_unlock();
continue;
}
* which can conditionally invoke cond_resched().
*/
console_may_schedule = 0;
- console_emit_next_record(con, text, ext_text, dropped_text);
+ console_emit_next_record(con, text, ext_text, dropped_text, &handover);
+ if (handover)
+ continue;
seq = con->seq;
- console_kthread_printing_exit();
-
- mutex_unlock(&con->lock);
+ __console_unlock();
}
con_printk(KERN_INFO, con, "printing thread stopped\n");
projects / kernel.git / commitdiff