printk: Use prb_first_seq() as base for 32bit seq macros

Note: This change only applies to 32bit architectures. On 64bit
      architectures the macros are NOPs.

Currently prb_next_seq() is used as the base for the 32bit seq
macros __u64seq_to_ulseq() and __ulseq_to_u64seq(). However, in
a follow-up commit, prb_next_seq() will need to make use of the
32bit seq macros.

Use prb_first_seq() as the base for the 32bit seq macros instead
because it is guaranteed to return 64bit sequence numbers without
relying on any 32bit seq macros.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240207134103.1357162-4-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>

diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringbuffer.c
index fde3386..49a82cc 100644 (file)
--- a/kernel/printk/printk_ringbuffer.c
+++ b/kernel/printk/printk_ringbuffer.c
@@ -1832,7 +1832,7 @@ static int prb_read(struct printk_ringbuffer *rb, u64 seq,
 }
 
 /* Get the sequence number of the tail descriptor. */
-static u64 prb_first_seq(struct printk_ringbuffer *rb)
+u64 prb_first_seq(struct printk_ringbuffer *rb)
 {
        struct prb_desc_ring *desc_ring = &rb->desc_ring;
        enum desc_state d_state;

diff --git a/kernel/printk/printk_ringbuffer.h b/kernel/printk/printk_ringbuffer.h
index 12f60c7..ee294aa 100644 (file)
--- a/kernel/printk/printk_ringbuffer.h
+++ b/kernel/printk/printk_ringbuffer.h
@@ -378,6 +378,7 @@ bool prb_read_valid(struct printk_ringbuffer *rb, u64 seq,
 bool prb_read_valid_info(struct printk_ringbuffer *rb, u64 seq,
                         struct printk_info *info, unsigned int *line_count);
 
+u64 prb_first_seq(struct printk_ringbuffer *rb);
 u64 prb_first_valid_seq(struct printk_ringbuffer *rb);
 u64 prb_next_seq(struct printk_ringbuffer *rb);
 
@@ -392,12 +393,12 @@ u64 prb_next_seq(struct printk_ringbuffer *rb);
 
 static inline u64 __ulseq_to_u64seq(struct printk_ringbuffer *rb, u32 ulseq)
 {
+       u64 rb_first_seq = prb_first_seq(rb);
        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
+        * sequence. It needs to be expanded to 64bit. Get the first sequence
         * number from the ringbuffer and fold it.
         *
         * Having a 32bit representation in the console is sufficient.
@@ -406,8 +407,7 @@ static inline u64 __ulseq_to_u64seq(struct printk_ringbuffer *rb, u32 ulseq)
         *
         * Also the access to the ring buffer is always safe.
         */
-       rb_next_seq = prb_next_seq(rb);
-       seq = rb_next_seq - (s32)((u32)rb_next_seq - ulseq);
+       seq = rb_first_seq - (s32)((u32)rb_first_seq - ulseq);
 
        return seq;
 }