printk: Convert console_drivers list to hlist (d9a4af56) · Commits · jan.koester / Linux

fs/proc/consoles.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -74,8 +74,9 @@ static void c_start(struct seq_file m, loff_t *pos)
		static void c_next(struct seq_file m, void v, loff_t pos)
		{
		struct console *con = v;

		++*pos;
		return con->next;
		return hlist_entry_safe(con->node.next, struct console, node);
		}

		static void c_stop(struct seq_file m, void v)

include/linux/console.h

+5 −3

Original line number	Diff line number	Diff line
		@@ -15,6 +15,7 @@
		#define _LINUX_CONSOLE_H_ 1

		#include <linux/atomic.h>
		#include <linux/list.h>
		#include <linux/types.h>

		struct vc_data;
		@@ -154,14 +155,16 @@ struct console {
		u64 seq;
		unsigned long dropped;
		void *data;
		struct console *next;
		struct hlist_node node;
		};

		extern struct hlist_head console_list;

		/*
		* for_each_console() allows you to iterate on each console
		*/
		#define for_each_console(con) \
		for (con = console_drivers; con != NULL; con = con->next)
		hlist_for_each_entry(con, &console_list, node)

		extern int console_set_on_cmdline;
		extern struct console *early_console;
		@@ -174,7 +177,6 @@ enum con_flush_mode {
		extern int add_preferred_console(char name, int idx, char options);
		extern void register_console(struct console *);
		extern int unregister_console(struct console *);
		extern struct console *console_drivers;
		extern void console_lock(void);
		extern int console_trylock(void);
		extern void console_unlock(void);

kernel/printk/printk.c

+55 −46

Original line number	Diff line number	Diff line
		@@ -79,13 +79,12 @@ int oops_in_progress;
		EXPORT_SYMBOL(oops_in_progress);

		/*
		* console_sem protects the console_drivers list, and also
		* provides serialisation for access to the entire console
		* driver system.
		* console_sem protects console_list and console->flags updates, and also
		* provides serialization for access to the entire console driver system.
		*/
		static DEFINE_SEMAPHORE(console_sem);
		struct console *console_drivers;
		EXPORT_SYMBOL_GPL(console_drivers);
		HLIST_HEAD(console_list);
		EXPORT_SYMBOL_GPL(console_list);

		/*
		* System may need to suppress printk message under certain
		@@ -2556,7 +2555,7 @@ static int console_cpu_notify(unsigned int cpu)
		* console_lock - lock the console system for exclusive use.
		*
		* Acquires a lock which guarantees that the caller has
		* exclusive access to the console system and the console_drivers list.
		* exclusive access to the console system and console_list.
		*
		* Can sleep, returns nothing.
		*/
		@@ -2576,7 +2575,7 @@ EXPORT_SYMBOL(console_lock);
		* console_trylock - try to lock the console system for exclusive use.
		*
		* Try to acquire a lock which guarantees that the caller has exclusive
		* access to the console system and the console_drivers list.
		* access to the console system and console_list.
		*
		* returns 1 on success, and 0 on failure to acquire the lock.
		*/
		@@ -2940,11 +2939,20 @@ void console_flush_on_panic(enum con_flush_mode mode)
		console_may_schedule = 0;

		if (mode == CONSOLE_REPLAY_ALL) {
		struct hlist_node *tmp;
		struct console *c;
		u64 seq;

		seq = prb_first_valid_seq(prb);
		for_each_console(c)
		/*
		* This cannot use for_each_console() because it's not established
		* that the current context has console locked and neither there is
		* a guarantee that there is no concurrency in that case.
		*
		* Open code it for documentation purposes and pretend that
		* it works.
		*/
		hlist_for_each_entry_safe(c, tmp, &console_list, node)
		c->seq = seq;
		}
		console_unlock();
		@@ -3081,6 +3089,9 @@ static void try_enable_default_console(struct console *newcon)
		(con->flags & CON_BOOT) ? "boot" : "", \
		con->name, con->index, ##__VA_ARGS__)

		#define console_first() \
		hlist_entry(console_list.first, struct console, node)

		/*
		* The console driver calls this routine during kernel initialization
		* to register the console printing procedure with printk() and to
		@@ -3140,8 +3151,8 @@ void register_console(struct console *newcon)
		* flag set and will be first in the list.
		*/
		if (preferred_console < 0) {
		if (!console_drivers \|\| !console_drivers->device \|\|
		console_drivers->flags & CON_BOOT) {
		if (hlist_empty(&console_list) \|\| !console_first()->device \|\|
		console_first()->flags & CON_BOOT) {
		try_enable_default_console(newcon);
		}
		}
		@@ -3173,16 +3184,18 @@ void register_console(struct console *newcon)
		* preferred driver at the head of the list.
		*/
		console_lock();
		if ((newcon->flags & CON_CONSDEV) \|\| console_drivers == NULL) {
		newcon->next = console_drivers;
		console_drivers = newcon;
		if (newcon->next)
		newcon->next->flags &= ~CON_CONSDEV;
		/* Ensure this flag is always set for the head of the list */
		if (hlist_empty(&console_list)) {
		/* Ensure CON_CONSDEV is always set for the head. */
		newcon->flags \|= CON_CONSDEV;
		hlist_add_head(&newcon->node, &console_list);

		} else if (newcon->flags & CON_CONSDEV) {
		/* Only the new head can have CON_CONSDEV set. */
		console_first()->flags &= ~CON_CONSDEV;
		hlist_add_head(&newcon->node, &console_list);

		} else {
		newcon->next = console_drivers->next;
		console_drivers->next = newcon;
		hlist_add_behind(&newcon->node, console_list.first);
		}

		newcon->dropped = 0;
		@@ -3209,16 +3222,18 @@ void register_console(struct console *newcon)
		if (bootcon_enabled &&
		((newcon->flags & (CON_CONSDEV \| CON_BOOT)) == CON_CONSDEV) &&
		!keep_bootcon) {
		for_each_console(con)
		struct hlist_node *tmp;

		hlist_for_each_entry_safe(con, tmp, &console_list, node) {
		if (con->flags & CON_BOOT)
		unregister_console(con);
		}
		}
		}
		EXPORT_SYMBOL(register_console);

		int unregister_console(struct console *console)
		{
		struct console *con;
		int res;

		con_printk(KERN_INFO, console, "disabled\n");
		@@ -3229,32 +3244,30 @@ int unregister_console(struct console *console)
		if (res > 0)
		return 0;

		res = -ENODEV;
		console_lock();
		if (console_drivers == console) {
		console_drivers=console->next;
		res = 0;
		} else {
		for_each_console(con) {
		if (con->next == console) {
		con->next = console->next;
		res = 0;
		break;
		}
		}

		/* Disable it unconditionally */
		console->flags &= ~CON_ENABLED;

		if (hlist_unhashed(&console->node)) {
		console_unlock();
		return -ENODEV;
		}

		if (res)
		goto out_disable_unlock;
		hlist_del_init(&console->node);

		/*
		* <HISTORICAL>
		* If this isn't the last console and it has CON_CONSDEV set, we
		* need to set it on the next preferred console.
		* </HISTORICAL>
		*
		* The above makes no sense as there is no guarantee that the next
		* console has any device attached. Oh well....
		*/
		if (console_drivers != NULL && console->flags & CON_CONSDEV)
		console_drivers->flags \|= CON_CONSDEV;
		if (!hlist_empty(&console_list) && console->flags & CON_CONSDEV)
		console_first()->flags \|= CON_CONSDEV;

		console->flags &= ~CON_ENABLED;
		console_unlock();
		console_sysfs_notify();

		@@ -3262,12 +3275,6 @@ int unregister_console(struct console *console)
		res = console->exit(console);

		return res;

		out_disable_unlock:
		console->flags &= ~CON_ENABLED;
		console_unlock();

		return res;
		}
		EXPORT_SYMBOL(unregister_console);

		@@ -3317,10 +3324,11 @@ void __init console_init(void)
		*/
		static int __init printk_late_init(void)
		{
		struct hlist_node *tmp;
		struct console *con;
		int ret;

		for_each_console(con) {
		hlist_for_each_entry_safe(con, tmp, &console_list, node) {
		if (!(con->flags & CON_BOOT))
		continue;

		@@ -3340,6 +3348,7 @@ static int __init printk_late_init(void)
		unregister_console(con);
		}
		}

		ret = cpuhp_setup_state_nocalls(CPUHP_PRINTK_DEAD, "printk:dead", NULL,
		console_cpu_notify);
		WARN_ON(ret < 0);