Bug 217955

Ever since 6.6.0-rc1 we've seen S3 and S2idle resume take 100ms longer because of resume_comsole. resume_console ordinarily takes only a few milliseconds, but now it's consistently 100ms. I've bisected the issue to this commit:

commit 9e70a5e109a4a23367810de09be826c52d27ee2f
Author: John Ogness <john.ogness@linutronix.de>
Date:   Mon Jul 17 21:52:06 2023 +0206

    printk: Add per-console suspended state
    
    Currently the global @console_suspended is used to determine if
    consoles are in a suspended state. Its primary purpose is to allow
    usage of the console_lock when suspended without causing console
    printing. It is synchronized by the console_lock.
    
    Rather than relying on the console_lock to determine suspended
    state, make it an official per-console state that is set within
    console->flags. This allows the state to be queried via SRCU.
    
    Remove @console_suspended. Console printing will still be avoided
    when suspended because console_is_usable() returns false when
    the new suspended flag is set for that console.

We are seeing this on roughly 2/3 of our machines, both on test systems and production systems.

I will attach sleepgraph timelines showing the effect. The dmesg logs and system data are contained in the html timelines and can be viewed by clicking the log and dmesg buttons.