Commit 90ad525c authored by John Ogness's avatar John Ogness Committed by Petr Mladek
Browse files

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: default avatarJohn Ogness <john.ogness@linutronix.de>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240207134103.1357162-4-john.ogness@linutronix.de


Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
parent 418ec196

kernel/printk/printk_ringbuffer.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

kernel/printk/printk_ringbuffer.h

+4 −4
Original line number Diff line number Diff line
@@ -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;

}