* might cause a system freeze when the console
* is used later.
* @pbufs: Pointer to the text buffer for this context
+ * @seq: The sequence number to print for this context
*/
struct nbcon_context {
/* members set by caller */
/* members set by acquire */
struct printk_buffers *pbufs;
+ u64 seq;
};
/**
* @node: hlist node for the console list
*
* @nbcon_state: State for nbcon consoles
+ * @nbcon_seq: Sequence number of the next record for nbcon to print
* @pbufs: Pointer to nbcon private buffer
*/
struct console {
/* nbcon console specific members */
atomic_t __private nbcon_state;
+ atomic_long_t __private nbcon_seq;
struct printk_buffers *pbufs;
};
*/
#include <linux/percpu.h>
#include <linux/console.h>
+#include "printk_ringbuffer.h"
#if defined(CONFIG_PRINTK) && defined(CONFIG_SYSCTL)
void __init printk_sysctl_init(void);
LOG_CONT = 8, /* text is a fragment of a continuation line */
};
+extern struct printk_ringbuffer *prb;
+
__printf(4, 0)
int vprintk_store(int facility, int level,
const struct dev_printk_info *dev_info,
u16 printk_parse_prefix(const char *text, int *level,
enum printk_info_flags *flags);
+u64 nbcon_seq_read(struct console *con);
+void nbcon_seq_force(struct console *con, u64 seq);
bool nbcon_alloc(struct console *con);
void nbcon_init(struct console *con);
void nbcon_free(struct console *con);
#define printk_safe_exit_irqrestore(flags) local_irq_restore(flags)
static inline bool printk_percpu_data_ready(void) { return false; }
+static inline u64 nbcon_seq_read(struct console *con) { return 0; }
+static inline void nbcon_seq_force(struct console *con, u64 seq) { }
static inline bool nbcon_alloc(struct console *con) { return false; }
static inline void nbcon_init(struct console *con) { }
static inline void nbcon_free(struct console *con) { }
return atomic_try_cmpxchg(&ACCESS_PRIVATE(con, nbcon_state), &cur->atom, new->atom);
}
+#ifdef CONFIG_64BIT
+
+#define __seq_to_nbcon_seq(seq) (seq)
+#define __nbcon_seq_to_seq(seq) (seq)
+
+#else /* CONFIG_64BIT */
+
+#define __seq_to_nbcon_seq(seq) ((u32)seq)
+
+static inline u64 __nbcon_seq_to_seq(u32 nbcon_seq)
+{
+ u64 seq;
+ u64 rb_next_seq;
+
+ /*
+ * The provided sequence is only the lower 32 bits of the ringbuffer
+ * sequence. It needs to be expanded to 64bit. Get the next sequence
+ * number from the ringbuffer and fold it.
+ *
+ * Having a 32bit representation in the console is sufficient.
+ * If a console ever gets more than 2^31 records behind
+ * the ringbuffer then this is the least of the problems.
+ *
+ * Also the access to the ring buffer is always safe.
+ */
+ rb_next_seq = prb_next_seq(prb);
+ seq = rb_next_seq - ((u32)rb_next_seq - nbcon_seq);
+
+ return seq;
+}
+
+#endif /* CONFIG_64BIT */
+
+/**
+ * nbcon_seq_read - Read the current console sequence
+ * @con: Console to read the sequence of
+ *
+ * Return: Sequence number of the next record to print on @con.
+ */
+u64 nbcon_seq_read(struct console *con)
+{
+ unsigned long nbcon_seq = atomic_long_read(&ACCESS_PRIVATE(con, nbcon_seq));
+
+ return __nbcon_seq_to_seq(nbcon_seq);
+}
+
+/**
+ * nbcon_seq_force - Force console sequence to a specific value
+ * @con: Console to work on
+ * @seq: Sequence number value to set
+ *
+ * Only to be used during init (before registration) or in extreme situations
+ * (such as panic with CONSOLE_REPLAY_ALL).
+ */
+void nbcon_seq_force(struct console *con, u64 seq)
+{
+ /*
+ * If the specified record no longer exists, the oldest available record
+ * is chosen. This is especially important on 32bit systems because only
+ * the lower 32 bits of the sequence number are stored. The upper 32 bits
+ * are derived from the sequence numbers available in the ringbuffer.
+ */
+ u64 valid_seq = max_t(u64, seq, prb_first_valid_seq(prb));
+
+ atomic_long_set(&ACCESS_PRIVATE(con, nbcon_seq), __seq_to_nbcon_seq(valid_seq));
+
+ /* Clear con->seq since nbcon consoles use con->nbcon_seq instead. */
+ con->seq = 0;
+}
+
+/**
+ * nbcon_seq_try_update - Try to update the console sequence number
+ * @ctxt: Pointer to an acquire context that contains
+ * all information about the acquire mode
+ * @new_seq: The new sequence number to set
+ *
+ * @ctxt->seq is updated to the new value of @con::nbcon_seq (expanded to
+ * the 64bit value). This could be a different value than @new_seq if
+ * nbcon_seq_force() was used or the current context no longer owns the
+ * console. In the later case, it will stop printing anyway.
+ */
+__maybe_unused
+static void nbcon_seq_try_update(struct nbcon_context *ctxt, u64 new_seq)
+{
+ unsigned long nbcon_seq = __seq_to_nbcon_seq(ctxt->seq);
+ struct console *con = ctxt->console;
+
+ if (atomic_long_try_cmpxchg(&ACCESS_PRIVATE(con, nbcon_seq), &nbcon_seq,
+ __seq_to_nbcon_seq(new_seq))) {
+ ctxt->seq = new_seq;
+ } else {
+ ctxt->seq = nbcon_seq_read(con);
+ }
+}
+
/**
* nbcon_context_try_acquire_direct - Try to acquire directly
* @ctxt: The context of the caller
else
ctxt->pbufs = con->pbufs;
+ /* Set the record sequence for this context to print. */
+ ctxt->seq = nbcon_seq_read(ctxt->console);
+
return true;
}
*
* nbcon_alloc() *must* be called and succeed before this function
* is called.
+ *
+ * This function expects that the legacy @con->seq has been set.
*/
void nbcon_init(struct console *con)
{
/* nbcon_alloc() must have been called and successful! */
BUG_ON(!con->pbufs);
+ nbcon_seq_force(con, con->seq);
nbcon_state_set(con, &state);
}
static struct printk_ringbuffer printk_rb_dynamic;
-static struct printk_ringbuffer *prb = &printk_rb_static;
+struct printk_ringbuffer *prb = &printk_rb_static;
/*
* We cannot access per-CPU data (e.g. per-CPU flush irq_work) before
if (mode == CONSOLE_REPLAY_ALL) {
struct console *c;
+ short flags;
int cookie;
u64 seq;
cookie = console_srcu_read_lock();
for_each_console_srcu(c) {
- /*
- * This is an unsynchronized assignment, but the
- * kernel is in "hope and pray" mode anyway.
- */
- c->seq = seq;
+ flags = console_srcu_read_flags(c);
+
+ if (flags & CON_NBCON) {
+ nbcon_seq_force(c, seq);
+ } else {
+ /*
+ * This is an unsynchronized assignment. On
+ * panic legacy consoles are only best effort.
+ */
+ c->seq = seq;
+ }
}
console_srcu_read_unlock(cookie);
}
struct console *c;
u64 last_diff = 0;
u64 printk_seq;
+ short flags;
int cookie;
u64 diff;
u64 seq;
for_each_console_srcu(c) {
if (con && con != c)
continue;
+
+ flags = console_srcu_read_flags(c);
+
/*
* If consoles are not usable, it cannot be expected
* that they make forward progress, so only increment
*/
if (!console_is_usable(c))
continue;
- printk_seq = c->seq;
+
+ if (flags & CON_NBCON) {
+ printk_seq = nbcon_seq_read(c);
+ } else {
+ printk_seq = c->seq;
+ }
+
if (printk_seq < seq)
diff += seq - printk_seq;
}
projects / linux.git / commitdiff