Hi Paul, On Tue, Sep 12, 2023 at 10:30 AM Paul E. McKenney <paulmck@xxxxxxxxxx> wrote: > On Tue, Sep 12, 2023 at 10:23:37AM +0200, Geert Uytterhoeven wrote: > > On Tue, Sep 12, 2023 at 10:14 AM Paul E. McKenney <paulmck@xxxxxxxxxx> wrote: > > > On Mon, Sep 11, 2023 at 07:54:52PM -0400, Liam R. Howlett wrote: > > > > * Paul E. McKenney <paulmck@xxxxxxxxxx> [230906 14:03]: > > > > > On Wed, Sep 06, 2023 at 01:29:54PM -0400, Liam R. Howlett wrote: > > > > > > * Paul E. McKenney <paulmck@xxxxxxxxxx> [230906 13:24]: > > > > > > > On Wed, Sep 06, 2023 at 11:23:25AM -0400, Liam R. Howlett wrote: > > > > > > > > (Adding Paul & Shanker to Cc list.. please see below for why) > > > > > > > > > > > > > > > > Apologies on the late response, I was away and have been struggling to > > > > > > > > get a working PPC32 test environment. > > > > > > > > > > > > > > > > * Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> [230829 12:42]: > > > > > > > > > Hi Liam, > > > > > > > > > > > > > > > > > > On Fri, 18 Aug 2023, Liam R. Howlett wrote: > > > > > > > > > > The current implementation of append may cause duplicate data and/or > > > > > > > > > > incorrect ranges to be returned to a reader during an update. Although > > > > > > > > > > this has not been reported or seen, disable the append write operation > > > > > > > > > > while the tree is in rcu mode out of an abundance of caution. > > > > > > > > > > > > > > > > ... > > > > > > > > > > > > > > > > > > ... > > > > > > > > > > > > > RCU-related configs: > > > > > > > > > > > > > > > > > > $ grep RCU .config > > > > > > > > > # RCU Subsystem > > > > > > > > > CONFIG_TINY_RCU=y > > > > > > I must have been asleep last time I looked at this. I was looking at > > > Tree RCU. Please accept my apologies for my lapse. :-/ > > > > > > However, Tiny RCU's call_rcu() also avoids enabling IRQs, so I would > > > have said the same thing, albeit after looking at a lot less RCU code. > > > > > > TL;DR: > > > > > > 1. Try making the __setup_irq() function's call to mutex_lock() > > > instead be as follows: > > > > > > if (!mutex_trylock(&desc->request_mutex)) > > > mutex_lock(&desc->request_mutex); > > > > > > This might fail if __setup_irq() has other dependencies on a > > > fully operational scheduler. > > > > > > 2. Move that ppc32 call to __setup_irq() much later, most definitely > > > after interrupts have been enabled and the scheduler is fully > > > operational. Invoking mutex_lock() before that time is not a > > > good idea. ;-) > > > > There is no call to __setup_irq() from arch/powerpc/? > > Glad it is not just me, given that I didn't see a direct call, either. So > later in this email, I asked Liam to put a WARN_ON_ONCE(irqs_disabled()) > just before that mutex_lock() in __setup_irq(). > > Either way, invoking mutex_lock() early in boot before interrupts have > been enabled is a bad idea. ;-) I'll add that WARN_ON_ONCE() too, and will report back later today... > > Note that there are (possibly different) issues seen on ppc32 and on arm32 > > (Renesas RZ/A in particular, but not on other Renesas ARM systems). > > > > I saw an issue on arm32 with cfeb6ae8bcb96ccf, but not with cfeb6ae8bcb96ccf^. > > Other people saw an issue on ppc32 with both cfeb6ae8bcb96ccf and > > cfeb6ae8bcb96ccf^. > > I look forward to hearing what is the issue in both cases. For RZ/A, my problem report is https://lore.kernel.org/all/3f86d58e-7f36-c6b4-c43a-2a7bcffd3bd@xxxxxxxxxxxxxx/ Thanks! Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
