Hi, Thomas,
On Thu, Aug 24, 2023 at 5:37 PM Thomas Gleixner tglx@linutronix.de wrote:
On Tue, Aug 22 2023 at 12:02, Huacai Chen wrote:
- This function may be called in NMI context, so we cannot use ktime_get_ns()
- and ktime_get_coarse_ns(). Instead, we use their inaccurate but safe friends
- ktime_get_mono_fast_ns() and ktime_get_seconds() which will cause rcu_state.
- jiffies_stall to be a little large than expected (harmless and safer).
What's inaccurate about ktime_get_mono_fast_ns()? Bogus comments are even worse than no comments.
ktime_get_mono_fast_ns() is not as accurate as ktime_get_ns(), I get this conclusion from:
* So if the update lowers the slope, readers who are forced to the * not yet updated second array are still using the old steeper slope.
*/ void rcu_cpu_stall_reset(void) {
u64 curr, last, delta;curr = ktime_get_mono_fast_ns();last = ktime_get_seconds() * NSEC_PER_SEC;So this will trigger a warning when someone debugs suspend with KGDB.
Yes, ktime_get_seconds() may cause a warning, I haven't noticed this before.
It seems the approach taken here seems to be to throw stuff at the wall and see what sticks.
I don't understand what's meaning, but I believe your advice in another thread is the best solution, so let me try.
Huacai
Thanks,
tglx