Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk
Pull printk updates from Petr Mladek:
- There is a situation when early console is not deregistered because
the preferred one matches a wrong entry. It caused messages to appear
twice.
This is the 2nd attempt to fix it. The first one was wrong, see the
commit c6c7d83b9c ('Revert "console: don't prefer first registered
if DT specifies stdout-path"').
The fix is coupled with some small code clean up. Well, the console
registration code would deserve a big one. We need to think about it.
- Do not lose information about the preemtive context when the console
semaphore is re-taken.
- Do not block CPU hotplug when someone else is already pushing
messages to the console.
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk:
printk: fix double printing with earlycon
printk: rename selected_console -> preferred_console
printk: fix name/type/scope of preferred_console var
printk: Correctly handle preemption in console_unlock()
printk: use console_trylock() in console_cpu_notify()
This commit is contained in:
Linus Torvalds
commit
9c35baf6ce
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@ -269,8 +269,8 @@ static struct console *exclusive_console;
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#define MAX_CMDLINECONSOLES 8
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static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
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static int console_cmdline_cnt;
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static int selected_console = -1;
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static int preferred_console = -1;
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int console_set_on_cmdline;
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EXPORT_SYMBOL(console_set_on_cmdline);
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@ -1906,24 +1906,38 @@ static int __add_preferred_console(char *name, int idx, char *options,
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* See if this tty is not yet registered, and
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* if we have a slot free.
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*/
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for (i = 0, c = console_cmdline;
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i < MAX_CMDLINECONSOLES && c->name[0];
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i++, c++) {
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for (i = 0, c = console_cmdline; i < console_cmdline_cnt; i++, c++) {
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if (strcmp(c->name, name) == 0 && c->index == idx) {
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if (!brl_options)
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selected_console = i;
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if (brl_options)
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return 0;
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/*
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* Maintain an invariant that will help to find if
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* the matching console is preferred, see
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* register_console():
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*
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* The last non-braille console is always
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* the preferred one.
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*/
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if (i != console_cmdline_cnt - 1)
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swap(console_cmdline[i],
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console_cmdline[console_cmdline_cnt - 1]);
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preferred_console = console_cmdline_cnt - 1;
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return 0;
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}
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}
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if (i == MAX_CMDLINECONSOLES)
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return -E2BIG;
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if (!brl_options)
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selected_console = i;
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preferred_console = i;
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strlcpy(c->name, name, sizeof(c->name));
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c->options = options;
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braille_set_options(c, brl_options);
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c->index = idx;
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console_cmdline_cnt++;
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return 0;
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}
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/*
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@ -2031,15 +2045,16 @@ void resume_console(void)
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* @cpu: unused
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*
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* If printk() is called from a CPU that is not online yet, the messages
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* will be spooled but will not show up on the console. This function is
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* called when a new CPU comes online (or fails to come up), and ensures
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* that any such output gets printed.
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* will be printed on the console only if there are CON_ANYTIME consoles.
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* This function is called when a new CPU comes online (or fails to come
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* up) or goes offline.
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*/
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static int console_cpu_notify(unsigned int cpu)
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{
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if (!cpuhp_tasks_frozen) {
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console_lock();
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console_unlock();
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/* If trylock fails, someone else is doing the printing */
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if (console_trylock())
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console_unlock();
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}
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return 0;
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}
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@ -2161,7 +2176,7 @@ void console_unlock(void)
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}
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/*
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* Console drivers are called under logbuf_lock, so
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* Console drivers are called with interrupts disabled, so
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* @console_may_schedule should be cleared before; however, we may
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* end up dumping a lot of lines, for example, if called from
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* console registration path, and should invoke cond_resched()
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@ -2169,11 +2184,15 @@ void console_unlock(void)
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* scheduling stall on a slow console leading to RCU stall and
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* softlockup warnings which exacerbate the issue with more
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* messages practically incapacitating the system.
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*
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* console_trylock() is not able to detect the preemptive
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* context reliably. Therefore the value must be stored before
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* and cleared after the the "again" goto label.
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*/
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do_cond_resched = console_may_schedule;
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again:
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console_may_schedule = 0;
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again:
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/*
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* We released the console_sem lock, so we need to recheck if
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* cpu is online and (if not) is there at least one CON_ANYTIME
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@ -2409,6 +2428,7 @@ void register_console(struct console *newcon)
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unsigned long flags;
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struct console *bcon = NULL;
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struct console_cmdline *c;
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static bool has_preferred;
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if (console_drivers)
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for_each_console(bcon)
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@ -2435,15 +2455,15 @@ void register_console(struct console *newcon)
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if (console_drivers && console_drivers->flags & CON_BOOT)
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bcon = console_drivers;
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if (preferred_console < 0 || bcon || !console_drivers)
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preferred_console = selected_console;
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if (!has_preferred || bcon || !console_drivers)
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has_preferred = preferred_console >= 0;
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/*
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* See if we want to use this console driver. If we
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* didn't select a console we take the first one
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* that registers here.
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*/
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if (preferred_console < 0) {
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if (!has_preferred) {
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if (newcon->index < 0)
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newcon->index = 0;
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if (newcon->setup == NULL ||
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@ -2451,18 +2471,29 @@ void register_console(struct console *newcon)
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newcon->flags |= CON_ENABLED;
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if (newcon->device) {
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newcon->flags |= CON_CONSDEV;
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preferred_console = 0;
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has_preferred = true;
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}
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}
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}
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/*
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* See if this console matches one we selected on
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* the command line.
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* See if this console matches one we selected on the command line.
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*
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* There may be several entries in the console_cmdline array matching
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* with the same console, one with newcon->match(), another by
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* name/index:
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*
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* pl011,mmio,0x87e024000000,115200 -- added from SPCR
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* ttyAMA0 -- added from command line
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*
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* Traverse the console_cmdline array in reverse order to be
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* sure that if this console is preferred then it will be the first
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* matching entry. We use the invariant that is maintained in
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* __add_preferred_console().
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*/
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for (i = 0, c = console_cmdline;
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i < MAX_CMDLINECONSOLES && c->name[0];
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i++, c++) {
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for (i = console_cmdline_cnt - 1; i >= 0; i--) {
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c = console_cmdline + i;
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if (!newcon->match ||
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newcon->match(newcon, c->name, c->index, c->options) != 0) {
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/* default matching */
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@ -2484,9 +2515,9 @@ void register_console(struct console *newcon)
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}
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newcon->flags |= CON_ENABLED;
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if (i == selected_console) {
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if (i == preferred_console) {
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newcon->flags |= CON_CONSDEV;
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preferred_console = selected_console;
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has_preferred = true;
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}
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break;
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}
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