Re: [PATCH v2] printk: ringbuffer: Improve prb_next_seq() performance
From: John Ogness <john.ogness@linutronix.de>
Date: 2021-10-27 15:48:46
Also in:
linux-mediatek, lkml
On 2021-10-27, Petr Mladek [off-list ref] wrote:
quoted hunk ↗ jump to hunk
diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringbuffer.c index 8a7b7362c0dd..24f47fbefbb5 100644 --- a/kernel/printk/printk_ringbuffer.c +++ b/kernel/printk/printk_ringbuffer.c@@ -474,8 +474,10 @@ static enum desc_state desc_read(struct prb_desc_ring *desc_ring, * state has been re-checked. A memcpy() for all of @desc * cannot be used because of the atomic_t @state_var field. */ - memcpy(&desc_out->text_blk_lpos, &desc->text_blk_lpos, - sizeof(desc_out->text_blk_lpos)); /* LMM(desc_read:C) */ + if (desc_out) { + memcpy(&desc_out->text_blk_lpos, &desc->text_blk_lpos, + sizeof(desc_out->text_blk_lpos)); /* LMM(desc_read:C) */ + } if (seq_out) *seq_out = info->seq; /* also part of desc_read:C */ if (caller_id_out)
You also need this hunk:
@@ -530,7 +530,8 @@ static enum desc_state desc_read(struct prb_desc_ring *desc_ring, state_val = atomic_long_read(state_var); /* LMM(desc_read:E) */ d_state = get_desc_state(id, state_val); out: - atomic_long_set(&desc_out->state_var, state_val); + if (desc_out) + atomic_long_set(&desc_out->state_var, state_val); return d_state; }
Sorry, I missed it in my last review. This time I build+boot tested the patch. With this hunk added: Reviewed-by: John Ogness <john.ogness@linutronix.de> John _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel