On 07/17/16 at 07:40am, Borislav Petkov wrote: > On Sat, Jul 16, 2016 at 06:44:25PM +0800, Dave Young wrote: > > ... > > > Mis-ratelimit cause critical userspace messages being lost, that is worse > > The current setting is quite generous so that all critical messages > should land in dmesg. Besides, we don't ratelimit during boot. The idea > is that userspace should switch to a different logging facility once the > system is up... which userspace does reportedly.
I would say avoiding ratelimit during boot make no much sense. Userspace can not write to /dev/kmsg when system_state == SYSTEM_BOOTING because init process has not run yet. > > IOW, /dev/kmsg should handle a relatively big logging amount without > ratelimiting. > > > than use off as default. Suppose we turn off devkmsg by default > > distributions > > can still turn on it with sysctl and for us who do not want the flooding we > > can > > use printk.devkmsg=off in kernel cmdline to override it. > > That part I cannot parse. I do not understand, care to elaborate a bit? Let me explain my comments, I means to set printk.devkmsg=off by default, userspace can set it to on by sysctl. User can provide kernel cmdline printk.devkmsg=off if he/she want. Or set printk.devkmsg=on by default to avoid break userspace, it is also fine. > > > Of course if we turn off it by default we can print a warning to alert user. > > > > BTW, for userspace messages maybe they should not go to same log buffer, > > maybe > > a separate log buffer for /dev/msg will be better. > > See above. > Thanks Dave