Messages in this thread Patch in this message | | | From | John Ogness <> | Subject | Re: [PATCH next v3 6/8] printk: ringbuffer: add finalization/extension support | Date | Mon, 31 Aug 2020 15:00:58 +0206 |
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This critical piece was missing from patch 6...
From 0b745d507f0c38e6d1612ed9468aa52845ca025b Mon Sep 17 00:00:00 2001 From: John Ogness <john.ogness@linutronix.de> Date: Mon, 31 Aug 2020 14:45:40 +0206 Subject: [PATCH] printk: ringbuffer: allow reading consistent descriptors
desc_read() will fail to read if a descriptor is in the desc_reserved queried state because such data would be inconsistent. However, since ("printk: ringbuffer: add finalization/extension support") the desc_reserved state can have the DESC_COMMIT_MASK flag set, in which case it _is_ consistent. And indeed, desc_reopen_last() is expecting a read in this case.
Allow desc_read() to read desc_reserved descriptors if the DESC_COMMIT_MASK flag is set.
Signed-off-by: John Ogness <john.ogness@linutronix.de> Reported-by: Andy Lavr <andy.lavr@gmail.com> Fixes: ("printk: ringbuffer: add finalization/extension support") --- kernel/printk/printk_ringbuffer.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringbuffer.c index 0731d5e2dddd..6ba7d3fc96f1 100644 --- a/kernel/printk/printk_ringbuffer.c +++ b/kernel/printk/printk_ringbuffer.c @@ -446,8 +446,10 @@ static enum desc_state desc_read(struct prb_desc_ring *desc_ring, /* Check the descriptor state. */ state_val = atomic_long_read(state_var); /* LMM(desc_read:A) */ d_state = get_desc_state(id, state_val); - if (d_state != desc_committed && d_state != desc_reusable) + if (d_state == desc_miss || + (d_state == desc_reserved && !(state_val & DESC_COMMIT_MASK))) { return d_state; + } /* * Guarantee the state is loaded before copying the descriptor -- 2.20.1
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