On Wed, Jun 20, 2018 at 12:30:58PM +0200, Thomas Gleixner wrote: > On Wed, 20 Jun 2018, Feng Tang wrote: > > > On Wed, Jun 20, 2018 at 12:16:36PM +0200, Thomas Gleixner wrote: > > > On Wed, 20 Jun 2018, Feng Tang wrote: > > > > On Wed, Jun 20, 2018 at 01:52:10AM +0200, Thomas Gleixner wrote: > > > > > > > > > > static DEFINE_STATIC_KEY_FALSE(__use_tsc); > > > > > +static DEFINE_STATIC_KEY_TRUE(tsc_early_enabled); > > > > > > > > One potential problem may be the several static_keys used here, > > > > the "__use_tsc", the "__sched_clock_stable", it may not be used > > > > very early in boot phase. As the the static_branch_enable() will > > > > use pageing related code while the paging is not setup ready yet. > > > > > > I know how static keys work and thats the reason for having the extra > > > conditional. The key is disabled at a point where paging is available. > > > > Maybe I'm wrong, for printk timestamp, it uses the local_clock() thus > > sched_clock_cpu() > > sched_clock_stable > > check the static_key "__sched_clock_stable" which is > > defined FALSE, and need a static_branch_enable() to > > take effect > > And that has nothing to do with this particular patch. Please read the rest > of the series, especially > > https://lkml.kernel.org/r/20180615174204.30581-5-pasha.tatas...@oracle.com Had not read that patch, thanks for the pointing. No problem now :)
- Feng
