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[All] (testing) Bumpe kernel to 6.6.14

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j1nx
2024-02-05 16:41:40 +00:00
parent 4fc5231981
commit fffa51ff5f
231 changed files with 23132 additions and 8386 deletions
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452
buildroot-external/patches/linux/0148-printk-nbcon-Introduce-printing-kthreads.patch Normal file
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@@ -0,0 +1,452 @@
From 858c2f115b2f1ef3e7757f28faa3a0e2fdf97fca Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Fri, 22 Sep 2023 14:12:21 +0000
Subject: [PATCH 148/195] printk: nbcon: Introduce printing kthreads
Provide the main implementation for running a printer kthread
per nbcon console that is takeover/handover aware.
The main print function nbcon_emit_next_record() will generate
a warning if a task other than the dedicated printer thread
tries to print using write_thread().
Co-developed-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Thomas Gleixner (Intel) <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
include/linux/console.h | 8 ++
kernel/printk/internal.h | 25 ++++++
kernel/printk/nbcon.c | 188 ++++++++++++++++++++++++++++++++++++++-
kernel/printk/printk.c | 31 +++++++
4 files changed, 249 insertions(+), 3 deletions(-)
diff --git a/include/linux/console.h b/include/linux/console.h
index 2583f13c25ba..5b5333faac7a 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -17,6 +17,7 @@
#include <linux/atomic.h>
#include <linux/bits.h>
#include <linux/rculist.h>
+#include <linux/rcuwait.h>
#include <linux/types.h>
struct vc_data;
@@ -296,12 +297,15 @@ struct nbcon_write_context {
* @node: hlist node for the console list
*
* @write_atomic: Write callback for atomic context
+ * @write_thread: Write callback for non-atomic context
* @driver_enter: Callback to begin synchronization with driver code
* @driver_exit: Callback to finish synchronization with driver code
* @nbcon_state: State for nbcon consoles
* @nbcon_seq: Sequence number of the next record for nbcon to print
* @pbufs: Pointer to nbcon private buffer
* @locked_port: True, if the port lock is locked by nbcon
+ * @kthread: Printer kthread for this console
+ * @rcuwait: RCU-safe wait object for @kthread waking
*/
struct console {
char name[16];
@@ -325,12 +329,16 @@ struct console {
/* nbcon console specific members */
bool (*write_atomic)(struct console *con,
struct nbcon_write_context *wctxt);
+ bool (*write_thread)(struct console *con,
+ struct nbcon_write_context *wctxt);
void (*driver_enter)(struct console *con, unsigned long *flags);
void (*driver_exit)(struct console *con, unsigned long flags);
atomic_t __private nbcon_state;
atomic_long_t __private nbcon_seq;
struct printk_buffers *pbufs;
bool locked_port;
+ struct task_struct *kthread;
+ struct rcuwait rcuwait;
};
#ifdef CONFIG_LOCKDEP
diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
index e2675981dfc5..4de36691009b 100644
--- a/kernel/printk/internal.h
+++ b/kernel/printk/internal.h
@@ -92,6 +92,7 @@ void nbcon_free(struct console *con);
enum nbcon_prio nbcon_get_default_prio(void);
void nbcon_atomic_flush_all(void);
bool nbcon_atomic_emit_next_record(struct console *con, bool *handover, int cookie);
+void nbcon_kthread_create(struct console *con);
/*
* Check if the given console is currently capable and allowed to print
@@ -110,6 +111,8 @@ static inline bool console_is_usable(struct console *con, short flags)
if (flags & CON_NBCON) {
if (!con->write_atomic)
return false;
+ if (!con->write_thread || !con->kthread)
+ return false;
} else {
if (!con->write)
return false;
@@ -126,12 +129,34 @@ static inline bool console_is_usable(struct console *con, short flags)
return true;
}
+/**
+ * nbcon_kthread_wake - Wake up a printk thread
+ * @con: Console to operate on
+ */
+static inline void nbcon_kthread_wake(struct console *con)
+{
+ /*
+ * Guarantee any new records can be seen by tasks preparing to wait
+ * before this context checks if the rcuwait is empty.
+ *
+ * The full memory barrier in rcuwait_wake_up() pairs with the full
+ * memory barrier within set_current_state() of
+ * ___rcuwait_wait_event(), which is called after prepare_to_rcuwait()
+ * adds the waiter but before it has checked the wait condition.
+ *
+ * This pairs with nbcon_kthread_func:A.
+ */
+ rcuwait_wake_up(&con->rcuwait); /* LMM(nbcon_kthread_wake:A) */
+}
+
#else
#define PRINTK_PREFIX_MAX 0
#define PRINTK_MESSAGE_MAX 0
#define PRINTKRB_RECORD_MAX 0
+static inline void nbcon_kthread_wake(struct console *con) { }
+static inline void nbcon_kthread_create(struct console *con) { }
#define printing_via_unlock (false)
/*
diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c
index c3ee245397f6..1becdfc7772c 100644
--- a/kernel/printk/nbcon.c
+++ b/kernel/printk/nbcon.c
@@ -5,8 +5,10 @@
#include <linux/kernel.h>
#include <linux/console.h>
#include <linux/delay.h>
+#include <linux/kthread.h>
#include <linux/slab.h>
#include <linux/serial_core.h>
+#include "printk_ringbuffer.h"
#include "internal.h"
/*
* Printk console printing implementation for consoles which does not depend
@@ -828,6 +830,7 @@ EXPORT_SYMBOL_GPL(nbcon_exit_unsafe);
/**
* 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.
@@ -841,7 +844,7 @@ EXPORT_SYMBOL_GPL(nbcon_exit_unsafe);
* 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;
@@ -891,9 +894,17 @@ static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt)
nbcon_state_read(con, &cur);
wctxt->unsafe_takeover = cur.unsafe_takeover;
- if (con->write_atomic)
+ if (use_atomic &&
+ con->write_atomic) {
done = con->write_atomic(con, wctxt);
+ } else if (!use_atomic &&
+ con->write_thread &&
+ con->kthread) {
+ WARN_ON_ONCE(con->kthread != current);
+ done = con->write_thread(con, wctxt);
+ }
+
if (!done) {
/*
* The emit was aborted, probably due to a loss of ownership.
@@ -929,6 +940,118 @@ static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt)
return nbcon_context_exit_unsafe(ctxt);
}
+/**
+ * nbcon_kthread_should_wakeup - Check whether a printer thread should wakeup
+ * @con: Console to operate on
+ * @ctxt: The acquire context that contains the state
+ * at console_acquire()
+ *
+ * Return: True if the thread should shutdown or if the console is
+ * allowed to print and a record is available. False otherwise.
+ *
+ * After the thread wakes up, it must first check if it should shutdown before
+ * attempting any printing.
+ */
+static bool nbcon_kthread_should_wakeup(struct console *con, struct nbcon_context *ctxt)
+{
+ bool is_usable;
+ short flags;
+ int cookie;
+
+ if (kthread_should_stop())
+ return true;
+
+ cookie = console_srcu_read_lock();
+ flags = console_srcu_read_flags(con);
+ is_usable = console_is_usable(con, flags);
+ console_srcu_read_unlock(cookie);
+
+ if (!is_usable)
+ return false;
+
+ /* Bring the sequence in @ctxt up to date */
+ ctxt->seq = nbcon_seq_read(con);
+
+ return prb_read_valid(prb, ctxt->seq, NULL);
+}
+
+/**
+ * nbcon_kthread_func - The printer thread function
+ * @__console: Console to operate on
+ */
+static int nbcon_kthread_func(void *__console)
+{
+ struct console *con = __console;
+ struct nbcon_write_context wctxt = {
+ .ctxt.console = con,
+ .ctxt.prio = NBCON_PRIO_NORMAL,
+ };
+ struct nbcon_context *ctxt = &ACCESS_PRIVATE(&wctxt, ctxt);
+ unsigned long flags;
+ short con_flags;
+ bool backlog;
+ int cookie;
+ int ret;
+
+wait_for_event:
+ /*
+ * Guarantee this task is visible on the rcuwait before
+ * checking the wake condition.
+ *
+ * The full memory barrier within set_current_state() of
+ * ___rcuwait_wait_event() pairs with the full memory
+ * barrier within rcuwait_has_sleeper().
+ *
+ * This pairs with rcuwait_has_sleeper:A and nbcon_kthread_wake:A.
+ */
+ ret = rcuwait_wait_event(&con->rcuwait,
+ nbcon_kthread_should_wakeup(con, ctxt),
+ TASK_INTERRUPTIBLE); /* LMM(nbcon_kthread_func:A) */
+
+ if (kthread_should_stop())
+ return 0;
+
+ /* Wait was interrupted by a spurious signal, go back to sleep. */
+ if (ret)
+ goto wait_for_event;
+
+ do {
+ backlog = false;
+
+ cookie = console_srcu_read_lock();
+
+ con_flags = console_srcu_read_flags(con);
+
+ if (console_is_usable(con, con_flags)) {
+ con->driver_enter(con, &flags);
+
+ /*
+ * Ensure this stays on the CPU to make handover and
+ * takeover possible.
+ */
+ cant_migrate();
+
+ if (nbcon_context_try_acquire(ctxt)) {
+ /*
+ * If the emit fails, this context is no
+ * longer the owner.
+ */
+ if (nbcon_emit_next_record(&wctxt, false)) {
+ nbcon_context_release(ctxt);
+ backlog = ctxt->backlog;
+ }
+ }
+
+ con->driver_exit(con, flags);
+ }
+
+ console_srcu_read_unlock(cookie);
+
+ } while (backlog);
+
+ goto wait_for_event;
+}
+
/* Track the nbcon emergency nesting per CPU. */
static DEFINE_PER_CPU(unsigned int, nbcon_pcpu_emergency_nesting);
static unsigned int early_nbcon_pcpu_emergency_nesting __initdata;
@@ -976,7 +1099,7 @@ static bool nbcon_atomic_emit_one(struct nbcon_write_context *wctxt)
* 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 false;
nbcon_context_release(ctxt);
@@ -1191,6 +1314,63 @@ void nbcon_cpu_emergency_exit(void)
printk_trigger_flush();
}
+/**
+ * nbcon_kthread_stop - Stop a printer thread
+ * @con: Console to operate on
+ */
+static void nbcon_kthread_stop(struct console *con)
+{
+ lockdep_assert_console_list_lock_held();
+
+ if (!con->kthread)
+ return;
+
+ kthread_stop(con->kthread);
+ con->kthread = NULL;
+}
+
+/**
+ * nbcon_kthread_create - Create a printer thread
+ * @con: Console to operate on
+ *
+ * If it fails, let the console proceed. The atomic part might
+ * be usable and useful.
+ */
+void nbcon_kthread_create(struct console *con)
+{
+ struct task_struct *kt;
+
+ lockdep_assert_console_list_lock_held();
+
+ if (!(con->flags & CON_NBCON) || !con->write_thread)
+ return;
+
+ if (con->kthread)
+ return;
+
+ /*
+ * Printer threads cannot be started as long as any boot console is
+ * registered because there is no way to synchronize the hardware
+ * registers between boot console code and regular console code.
+ */
+ if (have_boot_console)
+ return;
+
+ kt = kthread_run(nbcon_kthread_func, con, "pr/%s%d", con->name, con->index);
+ if (IS_ERR(kt)) {
+ con_printk(KERN_ERR, con, "failed to start printing thread\n");
+ return;
+ }
+
+ con->kthread = kt;
+
+ /*
+ * It is important that console printing threads are scheduled
+ * shortly after a printk call and with generous runtime budgets.
+ */
+ sched_set_normal(con->kthread, -20);
+}
+
/**
* nbcon_alloc - Allocate buffers needed by the nbcon console
* @con: Console to allocate buffers for
@@ -1237,6 +1417,7 @@ void nbcon_init(struct console *con)
/* nbcon_alloc() must have been called and successful! */
BUG_ON(!con->pbufs);
+ rcuwait_init(&con->rcuwait);
nbcon_seq_force(con, con->seq);
nbcon_state_set(con, &state);
}
@@ -1249,6 +1430,7 @@ void nbcon_free(struct console *con)
{
struct nbcon_state state = { };
+ nbcon_kthread_stop(con);
nbcon_state_set(con, &state);
/* Boot consoles share global printk buffers. */
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 11f26ad708d5..2499482dd08f 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2682,6 +2682,8 @@ void suspend_console(void)
void resume_console(void)
{
struct console *con;
+ short flags;
+ int cookie;
if (!console_suspend_enabled)
return;
@@ -2698,6 +2700,14 @@ void resume_console(void)
*/
synchronize_srcu(&console_srcu);
+ cookie = console_srcu_read_lock();
+ for_each_console_srcu(con) {
+ flags = console_srcu_read_flags(con);
+ if (flags & CON_NBCON)
+ nbcon_kthread_wake(con);
+ }
+ console_srcu_read_unlock(cookie);
+
pr_flush(1000, true);
}
@@ -3018,6 +3028,13 @@ static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handove
u64 printk_seq;
bool progress;
+ /*
+ * console_flush_all() is only for legacy consoles,
+ * unless the nbcon console has no kthread printer.
+ */
+ if ((flags & CON_NBCON) && con->kthread)
+ continue;
+
if (!console_is_usable(con, flags))
continue;
any_usable = true;
@@ -3313,9 +3330,23 @@ EXPORT_SYMBOL(console_stop);
void console_start(struct console *console)
{
+ short flags;
+
console_list_lock();
console_srcu_write_flags(console, console->flags | CON_ENABLED);
+ flags = console->flags;
console_list_unlock();
+
+ /*
+ * Ensure that all SRCU list walks have completed. The related
+ * printing context must be able to see it is enabled so that
+ * it is guaranteed to wake up and resume printing.
+ */
+ synchronize_srcu(&console_srcu);
+
+ if (flags & CON_NBCON)
+ nbcon_kthread_wake(console);
+
__pr_flush(console, 1000, true);
}
EXPORT_SYMBOL(console_start);
--
2.43.0