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printk: nbcon: Add context to usable() and emit()

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The nbcon consoles will have two callbacks to be used for
different contexts. In order to determine if an nbcon console
is usable, console_is_usable() must know if it is a context
that will need to use the optional write_atomic() callback.
Also, nbcon_emit_next_record() must know which callback it
needs to call.

Add an extra parameter @use_atomic to console_is_usable() and
nbcon_emit_next_record() to specify this.

Since so far only the write_atomic() callback exists,
@use_atomic is set to true for all call sites.

For legacy consoles, @use_atomic is not used.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240904120536.115780-5-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
This commit is contained in:
John Ogness 2024-09-04 14:11:23 +02:06 committed by Petr Mladek
parent 0e53e2d9f7
commit 6cb58cfebb
3 changed files with 27 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
kernel/printk/internal.h
View File

@ -97,7 +97,7 @@ bool nbcon_legacy_emit_next_record(struct console *con, bool *handover,
* which can also play a role in deciding if @con can be used to print
* records.
*/
static inline bool console_is_usable(struct console *con, short flags)
static inline bool console_is_usable(struct console *con, short flags, bool use_atomic)
{
if (!(flags & CON_ENABLED))
return false;
@ -106,7 +106,8 @@ static inline bool console_is_usable(struct console *con, short flags)
return false;
if (flags & CON_NBCON) {
if (!con->write_atomic)
/* The write_atomic() callback is optional. */
if (use_atomic && !con->write_atomic)
return false;
} else {
if (!con->write)
@ -149,7 +150,8 @@ static inline void nbcon_atomic_flush_pending(void) { }
static inline bool nbcon_legacy_emit_next_record(struct console *con, bool *handover,
int cookie) { return false; }
static inline bool console_is_usable(struct console *con, short flags) { return false; }
static inline bool console_is_usable(struct console *con, short flags,
bool use_atomic) { return false; }
#endif /* CONFIG_PRINTK */

34
kernel/printk/nbcon.c
View File

@ -922,6 +922,7 @@ EXPORT_SYMBOL_GPL(nbcon_reacquire_nobuf);
/**
* nbcon_emit_next_record - Emit a record in the acquired context
* @wctxt: The write context that will be handed to the write function
* @use_atomic: True if the write_atomic() callback is to be used
*
* Return: True if this context still owns the console. False if
* ownership was handed over or taken.
@ -935,7 +936,7 @@ EXPORT_SYMBOL_GPL(nbcon_reacquire_nobuf);
* When true is returned, @wctxt->ctxt.backlog indicates whether there are
* still records pending in the ringbuffer,
*/
static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt)
static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt, bool use_atomic)
{
struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt);
struct console *con = ctxt->console;
@ -946,6 +947,18 @@ static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt)
unsigned long con_dropped;
unsigned long dropped;
/*
* This function should never be called for consoles that have not
* implemented the necessary callback for writing: i.e. legacy
* consoles and, when atomic, nbcon consoles with no write_atomic().
* Handle it as if ownership was lost and try to continue.
*/
if (WARN_ON_ONCE((use_atomic && !con->write_atomic) ||
!(console_srcu_read_flags(con) & CON_NBCON))) {
nbcon_context_release(ctxt);
return false;
}
/*
* The printk buffers are filled within an unsafe section. This
* prevents NBCON_PRIO_NORMAL and NBCON_PRIO_EMERGENCY from
@ -980,17 +993,8 @@ static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt)
/* Initialize the write context for driver callbacks. */
nbcon_write_context_set_buf(wctxt, &pmsg.pbufs->outbuf[0], pmsg.outbuf_len);
if (con->write_atomic) {
if (use_atomic)
con->write_atomic(con, wctxt);
} else {
/*
* This function should never be called for legacy consoles.
* Handle it as if ownership was lost and try to continue.
*/
WARN_ON_ONCE(1);
nbcon_context_release(ctxt);
return false;
}
if (!wctxt->outbuf) {
/*
@ -1118,7 +1122,7 @@ static bool nbcon_atomic_emit_one(struct nbcon_write_context *wctxt)
* The higher priority printing context takes over responsibility
* to print the pending records.
*/
if (!nbcon_emit_next_record(wctxt))
if (!nbcon_emit_next_record(wctxt, true))
return false;
nbcon_context_release(ctxt);
@ -1219,7 +1223,7 @@ static int __nbcon_atomic_flush_pending_con(struct console *con, u64 stop_seq,
* handed over or taken over. In both cases the context is no
* longer valid.
*/
if (!nbcon_emit_next_record(&wctxt))
if (!nbcon_emit_next_record(&wctxt, true))
return -EAGAIN;
if (!ctxt->backlog) {
@ -1305,7 +1309,7 @@ static void __nbcon_atomic_flush_pending(u64 stop_seq, bool allow_unsafe_takeove
if (!(flags & CON_NBCON))
continue;
if (!console_is_usable(con, flags))
if (!console_is_usable(con, flags, true))
continue;
if (nbcon_seq_read(con) >= stop_seq)
@ -1490,7 +1494,7 @@ void nbcon_device_release(struct console *con)
* the console is usable throughout flushing.
*/
cookie = console_srcu_read_lock();
if (console_is_usable(con, console_srcu_read_flags(con)) &&
if (console_is_usable(con, console_srcu_read_flags(con), true) &&
prb_read_valid(prb, nbcon_seq_read(con), NULL)) {
/*
* If nbcon_atomic flushing is not available, fallback to

6
kernel/printk/printk.c
View File

@ -3071,7 +3071,7 @@ static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handove
u64 printk_seq;
bool progress;
if (!console_is_usable(con, flags))
if (!console_is_usable(con, flags, true))
continue;
any_usable = true;
@ -3773,7 +3773,7 @@ static int unregister_console_locked(struct console *console)
if (!console_is_registered_locked(console))
res = -ENODEV;
else if (console_is_usable(console, console->flags))
else if (console_is_usable(console, console->flags, true))
__pr_flush(console, 1000, true);
/* Disable it unconditionally */
@ -4043,7 +4043,7 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre
* that they make forward progress, so only increment
* @diff for usable consoles.
*/
if (!console_is_usable(c, flags))
if (!console_is_usable(c, flags, true))
continue;
if (flags & CON_NBCON) {