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printk: nbcon: Use nbcon consoles in console_flush_all()

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Allow nbcon consoles to print messages in the legacy printk()
caller context (printing via unlock) by integrating them into
console_flush_all(). The write_atomic() callback is used for
printing.

Provide nbcon_legacy_emit_next_record(), which acts as the
nbcon variant of console_emit_next_record(). Call this variant
within console_flush_all() for nbcon consoles. Since nbcon
consoles use their own @nbcon_seq variable to track the next
record to print, this also must be appropriately handled in
console_flush_all().

Note that the legacy printing logic uses @handover to detect
handovers for printing all consoles. For nbcon consoles,
handovers/takeovers occur on a per-console basis and thus do
not cause the console_flush_all() loop to abort.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-23-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
This commit is contained in:
John Ogness
2024-08-20 08:35:48 +02:06
committed by Petr Mladek
parent 97ea9bccfc
commit c158834b22
3 changed files with 105 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files
kernel/printk/printk.c
+12 -5
View File
@@ -1860,7 +1860,7 @@ static bool console_waiter;
* there may be a waiter spinning (like a spinlock). Also it must be
* ready to hand over the lock at the end of the section.
*/
static void console_lock_spinning_enable(void)
void console_lock_spinning_enable(void)
{
/*
* Do not use spinning in panic(). The panic CPU wants to keep the lock.
@@ -1899,7 +1899,7 @@ lockdep:
*
* Return: 1 if the lock rights were passed, 0 otherwise.
*/
static int console_lock_spinning_disable_and_check(int cookie)
int console_lock_spinning_disable_and_check(int cookie)
{
int waiter;
@@ -3021,13 +3021,20 @@ static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handove
cookie = console_srcu_read_lock();
for_each_console_srcu(con) {
short flags = console_srcu_read_flags(con);
u64 printk_seq;
bool progress;
if (!console_is_usable(con, flags))
continue;
any_usable = true;
progress = console_emit_next_record(con, handover, cookie);
if (flags & CON_NBCON) {
progress = nbcon_legacy_emit_next_record(con, handover, cookie);
printk_seq = nbcon_seq_read(con);
} else {
progress = console_emit_next_record(con, handover, cookie);
printk_seq = con->seq;
}
/*
* If a handover has occurred, the SRCU read lock
@@ -3037,8 +3044,8 @@ static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handove
return false;
/* Track the next of the highest seq flushed. */
if (con->seq > *next_seq)
*next_seq = con->seq;
if (printk_seq > *next_seq)
*next_seq = printk_seq;
if (!progress)
continue;