Messages in this thread | | | Subject | Re: Printk mulitple line message support | From | Joe Perches <> | Date | Mon, 14 Nov 2011 17:18:03 -0800 |
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On Tue, 2011-11-15 at 08:50 +0800, Huang Ying wrote: > On Mon, 2011-11-14 at 22:40 +0800, Joe Perches wrote: > > On Mon, 2011-11-14 at 14:58 +0800, Huang Ying wrote: > > > Hi, > > > > > > In most cases, printk only guarantees messages from different printk > > > calling will not be interleaved between each other. But many printk > > > users uses multiple line to form a complete message and call printk > > > for each line. So the following situation is possible for two printk > > > users running on two CPUs. > > > > > > line 1 of message from printk user1 > > > line 1 of message from printk user2 > > > line 2 of message from printk user1 > > > line 2 of message from printk user2 > > > > > > This makes kernel log hard to read. One possible solution to this > > > issue is to give a sequence number (or ID) to each complete message. > > > So the above lines will be: > > > > > > {1}line 1 of message from printk user1 > > > {2}line 1 of message from printk user2 > > > {1}line 2 of message from printk user1 > > > {2}line 2 of message from printk user2 > > > > > > Then some simple script can be used to group lines together according > > > to sequence number in lines. > > > > > > What do you think about that? > > > > This makes the typical multi-part but non-interleaved > > output difficult to read. > > With a simple script, we can strip out the sequence # easily. > > > How about determining if there is interleaving and > > emitting sequence # only in those cases? > > > > Perhaps test the atomic for the last sequence #. > > So we will have no sequence # prefix for printk user1's lines if printk > user 2 comes in the middle? Something as follow? > > line 1 of message from printk user1 > {2}line 1 of message from printk user2 > line 2 of message from printk user1 > {2}line 2 of message from printk user2 > > This will make it hard for a script to sort the lines. Where should it > insert lines from printk user2 in the sort result?
90+% it's the previous line.
I believe you are not solving any real problem with pr_<level>_ml.
Most all interleaved complete line uses have some pr_fmt prefix that distinguishes between the sources.
A perhaps larger problem is interleaved partial lines with pr_cont.
I believe that an initiator/terminator is necessary for reassembly. Something that could be used with pr_<level>, dev_<level>, netdev_<level>, et al.
mp_start(&cookie) pr_<level>(fmt, ...); pr_mp_cont(&cookie, fmt, ...); pr_mp_cont(&cookie, fmt "\n", ...); mp_end(&cookie);
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