On Tue, Mar 12, 2024 at 10:01:00PM +0100, Frederic Weisbecker wrote: > Le Tue, Mar 12, 2024 at 01:32:03PM -0700, Florian Fainelli a écrit : > > Hi Boqun, > > > > On 3/8/24 09:15, Boqun Feng wrote: > > > Hi Linus, > > > > > > Please pull this for the RCU changes of v6.9: > > > > > > The following changes since commit 41bccc98fb7931d63d03f326a746ac4d429c1dd3: > > > > > > Linux 6.8-rc2 (2024-01-28 17:01:12 -0800) > > > > > > are available in the Git repository at: > > > > > > git://git.kernel.org/pub/scm/linux/kernel/git/boqun/linux.git tags/rcu.next.v6.9 > > > > > > for you to fetch changes up to 3add00be5fe5810d7aa5ec3af8b6a245ef33144b: > > > > > > Merge branches 'rcu-doc.2024.02.14a', 'rcu-nocb.2024.02.14a', 'rcu-exp.2024.02.14a', 'rcu-tasks.2024.02.26a' and 'rcu-misc.2024.02.14a' into rcu.2024.02.26a (2024-02-26 17:37:25 -0800) > > > > > > > > > Two merge conflicts were detected by linux-next: > > > > > > * https://lore.kernel.org/lkml/20240226135745.12ac854d@xxxxxxxxxxxxxxxx/ > > > * https://lore.kernel.org/lkml/20240227125522.2bdbe6be@xxxxxxxxxxxxxxxx/ > > > > > > These conflict resolutions from linux-next look good to me, plus I made > > > my own resolutions at branch merge/rcu.2024.02.27a for your reference. > > > > > > > > > Some highlights of the changes: > > > > > > * Eliminates deadlocks involving do_exit() and RCU tasks, by Paul: > > > Instead of SRCU read side critical sections, now a percpu list is used > > > in do_exit() for scaning yet-to-exit tasks. > > > > > > * Fixes a deadlock due to the dependency between workqueue and RCU > > > expedited grace period, reported by Anna-Maria Behnsen and Thomas > > > Gleixner and fixed by Frederic: Now RCU expedited always uses its own > > > kthread worker instead of a workqueue. > > > > At least one device in my test farm (ARM 32-bit) has consistently shown a > > very long boot, and some others are intermittently affected. This > > consistently looks like this on most of my devices: > > > > [ 2.450351] bcmgenet f0480000.ethernet: GENET 5.0 EPHY: 0x0000 > > [ 2.547562] ata1: SATA link down (SStatus 0 SControl 300) > > [ 162.107264] unimac-mdio unimac-mdio.0: Broadcom UniMAC MDIO bus > > > > this gets flagged by my boot script as a boot failure since we exceeded the > > 30 seconds timeout given to boot a kernel to a prompt. > > > > It has been somewhat difficult to get a reliable bisection going on, but > > what I am sure of is that e5a3878c947ceef7b6ab68fdc093f3848059842c~1 does > > not expose the problem for 10 consecutive boots, while I *might* see it at > > e5a3878c947ceef7b6ab68fdc093f3848059842c and beyond. > > > > Any clues what is going on here? > > I understand it doesn't reliably reproduce. But is there any chance you could > test that alone? > > 0bb11a372fc8 (rcu-tasks: Maintain real-time response in rcu_tasks_postscan()) > > And if it reproduces there try a bisection? > > git bisect bad 0bb11a372fc8d7006b4d0f42a2882939747bdbff > git bisect good 41bccc98fb7931d63d03f326a746ac4d429c1dd3 Good point! Is this kernel built with CONFIG_PREEMPT_RT=y and CONFIG_TASKS_RCU=y? Either way, is there also a large number of tasks exiting at this point during boot? Thanx, Paul
