Messages in this thread Patch in this message | | | Subject | Re: [PATCH/RFC v5 4/5]: core: Add dump device to call on oopses and panics | From | David Woodhouse <> | Date | Mon, 30 Nov 2009 10:23:31 +0000 |
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On Mon, 2009-11-30 at 10:51 +0200, Artem Bityutskiy wrote: > On Mon, 2009-11-30 at 08:46 +0100, Jörn Engel wrote: > > On Mon, 30 November 2009 09:27:51 +0200, Artem Bityutskiy wrote: > > > > > > To me it looks like 'log_end' is not supposed to wrap. What makes you > > > think it can? In which cases it can? > > > > It is a 32bit variable. Would do you expect happens once you reach > > 0xffffffff and add 1? > > Yes, now I see log_end is an ever increasing variable. > > How about this patch on top of the existing one (untested):
I suspect you should be modelling this more closely on the code in do_syslog() for case 3. The end is at (log_end & LOG_BUF_MASK), and you have (logged_chars) to write.
This mean that you won't write messages to the log which were 'cleared' by 'dmesg -c', but that's acceptable, I think.
Why are you setting s1 to "" in the case where l1 is zero, btw? Can't it be NULL?
diff --git a/kernel/printk.c b/kernel/printk.c index f711b99..d150c57 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -1486,26 +1486,33 @@ static const char *kmsg_to_str(enum kmsg_dump_reason reason) */ void kmsg_dump(enum kmsg_dump_reason reason) { - unsigned long len = ACCESS_ONCE(log_end); + unsigned long end; + unsigned chars; struct kmsg_dumper *dumper; const char *s1, *s2; unsigned long l1, l2; unsigned long flags; - s1 = ""; - l1 = 0; - s2 = log_buf; - l2 = len; - - /* Have we rotated around the circular buffer? */ - if (len > log_buf_len) { - unsigned long pos = len & LOG_BUF_MASK; + /* Theoretically, the log could move on after we do this, but + there's not a log we can do about that. The new messages + will overwrite the start of what we dump. */ + spin_lock_irqsave(&logbuf_lock, flags); + end = log_end & LOG_BUF_MASK; + chars = logged_chars; + spin_unlock_irqrestore(&logbuf_lock, flags); - s1 = log_buf + pos; - l1 = log_buf_len - pos; + if (logged_chars > end) { + s1 = log_buf + log_buf_len - logged_chars + end; + l1 = logged_chars - end; s2 = log_buf; - l2 = pos; + l2 = end; + } else { + s1 = ""; + l1 = 0; + + s2 = log_buf + end - logged_chars; + l2 = logged_chars; } if (!spin_trylock_irqsave(&dump_list_lock, flags)) {
-- David Woodhouse Open Source Technology Centre David.Woodhouse@intel.com Intel Corporation
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