From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: John Ogness <john.ogness@linutronix.de>
Cc: Andrea Parri <parri.andrea@gmail.com>,
Petr Mladek <pmladek@suse.com>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Paul McKenney <paulmck@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
Steven Rostedt <rostedt@goodmis.org>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH v2 5/7][next] printk: ringbuffer: add finalization/extension support
Date: Wed, 26 Aug 2020 19:01:13 +0900 [thread overview]
Message-ID: <20200826100113.GA8849@jagdpanzerIV.localdomain> (raw)
In-Reply-To: <87lfi1ls2g.fsf@jogness.linutronix.de>
On (20/08/26 10:45), John Ogness wrote:
> On 2020-08-24, John Ogness <john.ogness@linutronix.de> wrote:
> > @@ -1157,6 +1431,14 @@ bool prb_reserve(struct prb_reserved_entry *e, struct printk_ringbuffer *rb,
> > goto fail;
> > }
> >
> > + /*
> > + * New data is about to be reserved. Once that happens, previous
> > + * descriptors are no longer able to be extended. Finalize the
> > + * previous descriptor now so that it can be made available to
> > + * readers (when committed).
> > + */
> > + desc_finalize(desc_ring, DESC_ID(id - 1));
> > +
> > d = to_desc(desc_ring, id);
> >
> > /*
>
> Apparently this is not enough to guarantee that past descriptors are
> finalized. I am able to reproduce a scenario where the finalization of a
> certain descriptor never happens. That leaves the descriptor permanently
> in the reserved queried state, which prevents any new records from being
> created. I am investigating.
Good to know. I also run into problems:
- broken dmesg (and broken journalctl -f /dev/kmsg poll) and broken
syslog read
$ strace dmesg
...
openat(AT_FDCWD, "/dev/kmsg", O_RDONLY|O_NONBLOCK) = 3
lseek(3, 0, SEEK_DATA) = 0
read(3, 0x55dda8c240a8, 8191) = -1 EAGAIN (Resource temporarily unavailable)
close(3) = 0
syslog(10 /* SYSLOG_ACTION_SIZE_BUFFER */) = 524288
mmap(NULL, 528384, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f43ea847000
syslog(3 /* SYSLOG_ACTION_READ_ALL */, "", 524296) = 0
munmap(0x7f43ea847000, 528384) = 0
...
-ss
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next prev parent reply other threads:[~2020-08-26 10:01 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-24 10:35 [PATCH v2 0/7][next] printk: reimplement LOG_CONT handling John Ogness
2020-08-24 10:35 ` [PATCH v2 1/7][next] printk: ringbuffer: rename DESC_COMMITTED_MASK flag John Ogness
2020-08-25 17:09 ` Petr Mladek
2020-08-24 10:35 ` [PATCH v2 2/7][next] printk: ringbuffer: change representation of reusable John Ogness
2020-08-25 17:10 ` Petr Mladek
2020-08-24 10:35 ` [PATCH v2 3/7][next] printk: ringbuffer: relocate get_data() John Ogness
2020-08-25 17:14 ` Petr Mladek
2020-08-24 10:35 ` [PATCH v2 4/7][next] printk: ringbuffer: add BLK_DATALESS() macro John Ogness
2020-08-25 17:24 ` Petr Mladek
2020-08-24 10:35 ` [PATCH v2 5/7][next] printk: ringbuffer: add finalization/extension support John Ogness
2020-08-26 8:39 ` John Ogness
2020-08-26 10:01 ` Sergey Senozhatsky [this message]
2020-08-26 12:37 ` John Ogness
2020-08-26 15:07 ` Petr Mladek
2020-08-27 9:58 ` John Ogness
2020-08-27 15:17 ` Petr Mladek
2020-08-28 7:21 ` Petr Mladek
2020-08-28 10:01 ` John Ogness
2020-08-27 12:50 ` Petr Mladek
2020-08-27 14:28 ` John Ogness
2020-08-24 10:35 ` [PATCH v2 6/7][next] printk: reimplement log_cont using record extension John Ogness
2020-08-24 10:35 ` [PATCH v2 7/7][next] scripts/gdb: support printk finalized records John Ogness
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