7 #include <linux/console.h>
25  * Printk console printing implementation for consoles which does not depend
28  * The state of the console is maintained in the "nbcon_state" atomic
31  * The console is locked when:
34  *     console. Only higher priority contexts are allowed to take over the
35  *     lock. A value of 0 (NBCON_PRIO_NONE) means the console is not locked.
37  *   - The 'cpu' field denotes on which CPU the console is locked. It is used
49  *   - The 'unsafe' field allows to take over the console in a safe way in the
51  *     shared resources or when the console device is manipulated. It can be
52  *     cleared, for example, after emitting one character when the console
56  *     console in an unsafe state. The console will stay in the unsafe state
61  *   1) Direct acquire when the console is not owned or is owned by a lower
65  *      when the current owner has lower priority and the console is in an
73  *           console.
80  *           console state.
82  *        b) Gives up console ownership by clearing the 'prio' field.
85  *      console is an unsafe state. It is used only in panic() by the final
94  * All operations on @console::nbcon_state are atomic cmpxchg based to
105  *   - Whether to spin-wait if there is already an owner and the console is
121  * nbcon_state_set - Helper function to set the console state
122  * @con:	Console to update
125  * Only to be used when the console is not yet or no longer visible in the
128 static inline void nbcon_state_set(struct console *con, struct nbcon_state *new)  in nbcon_state_set()
134  * nbcon_state_read - Helper function to read the console state
135  * @con:	Console to read
138 static inline void nbcon_state_read(struct console *con, struct nbcon_state *state)  in nbcon_state_read()
144  * nbcon_state_try_cmpxchg() - Helper function for atomic_try_cmpxchg() on console state
145  * @con:	Console to update
151 static inline bool nbcon_state_try_cmpxchg(struct console *con, struct nbcon_state *cur,  in nbcon_state_try_cmpxchg()
158  * nbcon_seq_read - Read the current console sequence
159  * @con:	Console to read the sequence of
163 u64 nbcon_seq_read(struct console *con)  in nbcon_seq_read()
171  * nbcon_seq_force - Force console sequence to a specific value
172  * @con:	Console to work on
178 void nbcon_seq_force(struct console *con, u64 seq)  in nbcon_seq_force()
192  * nbcon_seq_try_update - Try to update the console sequence number
200  * console. In the later case, it will stop printing anyway.
205 	struct console *con = ctxt->console;  in nbcon_seq_try_update()
218  * @cur:	The current console state
220  * Acquire the console when it is released. Also acquire the console when
221  * the current owner has a lower priority and the console is in a safe state.
233  *	-EBUSY:		The current owner has a lower priority but the console
241 	struct console *con = ctxt->console;  in nbcon_context_try_acquire_direct()
246 		 * Panic does not imply that the console is owned. However, it  in nbcon_context_try_acquire_direct()
262 		 * The console should never be safe for a direct acquire  in nbcon_context_try_acquire_direct()
303 	 * Event #3 occurs when panic() has flushed the console.  in nbcon_waiter_matches()
315  * @cur:	The current console state
318  * It is called when the console is in an unsafe state. The current
319  * owner will release the console on exit from the unsafe region.
321  * Return:	0 on success and @cur is updated to the new console state.
329  *	-EBUSY:		The console is still locked. The caller should
339 	struct console *con = ctxt->console;  in nbcon_context_try_acquire_requested()
378 	/* Handover success. This context now owns the console. */  in nbcon_context_try_acquire_requested()
385  * @cur:	The current console state
388  * than the current owner and the console is in an unsafe state.
392  * the request. Then it waits until the current owner releases the console,
396  * region and releases the console. It does not touch the "req_prio" field
397  * so that the console stays reserved for the waiter.
406  *			console or the handover request.
410  *			willing to wait (zero timeout). Or the console does
422 	struct console *con = ctxt->console;  in nbcon_context_try_acquire_handover()
439 	 * Console stays unsafe after an unsafe takeover until re-initialized.  in nbcon_context_try_acquire_handover()
451 	 * the console directly when the current state has been modified.  in nbcon_context_try_acquire_handover()
460 	/* Wait until there is no owner and then acquire the console. */  in nbcon_context_try_acquire_handover()
485 		 * the console or the handover request.  in nbcon_context_try_acquire_handover()
515  * @cur:	The current console state
517  * Acquire the console even in the unsafe state.
528 	struct console *con = ctxt->console;  in nbcon_context_try_acquire_hostile()
560  * nbcon_context_try_acquire - Try to acquire nbcon console
564  * Return:	True if the console was acquired. False otherwise.
567  * caller should check the current console state to see if it is
569  * the console is not in an unsafe state.
574 	struct console *con = ctxt->console;  in nbcon_context_try_acquire()
604 	ctxt->seq = nbcon_seq_read(ctxt->console);  in nbcon_context_try_acquire()
633 	 * 4. [Task A] gets running on [CPU X] and sees that the console is  in nbcon_owner_matches()
648  * nbcon_context_release - Release the console
654 	struct console *con = ctxt->console;  in nbcon_context_release()
681  * @cur:	The current console state
683  * Return:	True if this context still owns the console. False if
691  * It can be called inside an unsafe section when the console is just
700  * the console and is no longer allowed to go forward. In this case it must
708 	/* Make sure this context still owns the console. */  in nbcon_context_can_proceed()
712 	/* The console owner can proceed if there is no waiter. */  in nbcon_context_can_proceed()
717 	 * A console owner within an unsafe region is always allowed to  in nbcon_context_can_proceed()
738 	 * outermost callsite must make the final decision whether console  in nbcon_context_can_proceed()
742 	 * The calling context no longer owns the console so go back all the  in nbcon_context_can_proceed()
753  * Return:	True if this context still owns the console. False if
760  * It can be called inside an unsafe section when the console is just
768  * the console and is no longer allowed to go forward. In this case it must
775 	struct console *con = ctxt->console;  in nbcon_can_proceed()
793  *		owns the console. Otherwise false if ownership was handed
796  * This function allows console owners to modify the unsafe status of the
797  * console.
800  * the console and is no longer allowed to go forward. In this case it must
808 	struct console *con = ctxt->console;  in __nbcon_context_update_unsafe()
838 	struct console *con = ctxt->console;  in nbcon_write_context_set_buf()
851  * Return:	True if this context still owns the console. False if
855  * the console and is no longer allowed to go forward. In this case it must
875  * Return:	True if this context still owns the console. False if
879  * the console and is no longer allowed to go forward. In this case it must
896  * nbcon_reacquire_nobuf - Reacquire a console after losing ownership
928  * Return:	True if this context still owns the console. False if
932  * the console and is no longer allowed to go forward. In this case it must
935  * wants to do more it must reacquire the console first.
943 	struct console *con = ctxt->console;  in nbcon_emit_next_record()
1047 	 * dropped count for the console.  in nbcon_emit_next_record()
1071  * nbcon_emit_one - Print one record for an nbcon console using the
1079  *		False, when there is no pending record, or when the console
1084  * This is an internal helper to handle the locking of the console before
1090 	struct console *con = ctxt->console;  in nbcon_emit_one()
1108 	 * nbcon_emit_next_record() returns false when the console was  in nbcon_emit_one()
1129  * @con:	Console to operate on
1132  * Return:	True if the thread should shutdown or if the console is
1138 static bool nbcon_kthread_should_wakeup(struct console *con, struct nbcon_context *ctxt)  in nbcon_kthread_should_wakeup()
1163  * @__console:	Console to operate on
1169 	struct console *con = __console;  in nbcon_kthread_func()
1171 		.ctxt.console	= con,  in nbcon_kthread_func()
1222  * nbcon_irq_work - irq work to wake console printer thread
1227 	struct console *con = container_of(irq_work, struct console, irq_work);  in nbcon_irq_work()
1254 	struct console *con;  in nbcon_kthreads_wake()
1277  * nbcon_kthread_stop - Stop a console printer thread
1278  * @con:	Console to operate on
1280 void nbcon_kthread_stop(struct console *con)  in nbcon_kthread_stop()
1292  * nbcon_kthread_create - Create a console printer thread
1293  * @con:	Console to operate on
1301  * be fatal for console registration.
1307 bool nbcon_kthread_create(struct console *con)  in nbcon_kthread_create()
1325 	 * It is important that console printing threads are scheduled  in nbcon_kthread_create()
1367  * Return:	The nbcon_prio to use for acquiring an nbcon console in this
1389  * nbcon_legacy_emit_next_record - Print one record for an nbcon console
1391  * @con:	The console to print on
1409  *		False, when there is no pending record, or when the console
1415  * on nbcon consoles from legacy context (printing via console unlocking).
1418 bool nbcon_legacy_emit_next_record(struct console *con, bool *handover,  in nbcon_legacy_emit_next_record()
1426 	ctxt->console	= con;  in nbcon_legacy_emit_next_record()
1454  * __nbcon_atomic_flush_pending_con - Flush specified nbcon console using its
1456  * @con:			The nbcon console to flush
1465  *	-EPERM:		Unable to acquire console ownership.
1473  * this context is not allowed to acquire the console. When -ENOENT is
1477 static int __nbcon_atomic_flush_pending_con(struct console *con, u64 stop_seq,  in __nbcon_atomic_flush_pending_con()
1484 	ctxt->console			= con;  in __nbcon_atomic_flush_pending_con()
1494 		 * nbcon_emit_next_record() returns false when the console was  in __nbcon_atomic_flush_pending_con()
1514  * nbcon_atomic_flush_pending_con - Flush specified nbcon console using its
1516  * @con:			The nbcon console to flush
1525 static void nbcon_atomic_flush_pending_con(struct console *con, u64 stop_seq,  in nbcon_atomic_flush_pending_con()
1534 	 * Atomic flushing does not use console driver synchronization (i.e.  in nbcon_atomic_flush_pending_con()
1537 	 * a driver that will deadlock trying to acquire console ownership.  in nbcon_atomic_flush_pending_con()
1577 	struct console *con;  in __nbcon_atomic_flush_pending()
1661  * nbcon_alloc - Allocate and init the nbcon console specific data
1662  * @con:	Console to initialize
1664  * Return:	True if the console was fully allocated and initialized.
1667  * When allocation and init was successful, the console must be properly
1670 bool nbcon_alloc(struct console *con)  in nbcon_alloc()
1692 		 * Boot console printing is synchronized with legacy console  in nbcon_alloc()
1717  * nbcon_free - Free and cleanup the nbcon console specific data
1718  * @con:	Console to free/cleanup nbcon data
1720 void nbcon_free(struct console *con)  in nbcon_free()
1737  * nbcon_device_try_acquire - Try to acquire nbcon console and enter unsafe
1739  * @con:	The nbcon console to acquire
1743  * Return:	True if the console was acquired. False otherwise.
1745  * Console drivers will usually use their own internal synchronization
1746  * mechasism to synchronize between console printing and non-printing
1747  * activities (such as setting baud rates). However, nbcon console drivers
1752  * This function acquires the nbcon console using priority NBCON_PRIO_NORMAL
1755 bool nbcon_device_try_acquire(struct console *con)  in nbcon_device_try_acquire()
1762 	ctxt->console	= con;  in nbcon_device_try_acquire()
1776  * nbcon_device_release - Exit unsafe section and release the nbcon console
1777  * @con:	The nbcon console acquired in nbcon_device_try_acquire()
1779 void nbcon_device_release(struct console *con)  in nbcon_device_release()
1791 	 * This context must flush any new records added while the console  in nbcon_device_release()
1793 	 * console_srcu_read_lock must be taken to ensure the console is  in nbcon_device_release()