Subject: Re: linux-next: build failure after merge of the tip tree

From: Peter Zijlstra <[email-masked]>
Date: Thu, 7 Nov 2024 15:12:12 +0100

On Fri, Nov 08, 2024 at 12:04:32AM +1100, Stephen Rothwell wrote:
> Hi Peter,
> 
> On Thu, 7 Nov 2024 11:34:14 +0100 Peter Zijlstra <[email-masked]> wrote:
> >
> > On Thu, Nov 07, 2024 at 06:24:11PM +1100, Stephen Rothwell wrote:
> > So I can't get RUST=y, even though make rustavailable is happy.
> > 
> > make LLVM=-19 allmodconfig does not get me RUST=y
> > 
> > I started out with tip/master, tried adding rust-next, then kbuild-next
> > gave up and tried next/master. Nada.
> 
> Just on Linus' tree allmodconfig gives me:
> 
> $ grep RUST .config
> CONFIG_RUSTC_VERSION=108100
> CONFIG_RUST_IS_AVAILABLE=y
> CONFIG_RUSTC_LLVM_VERSION=180108
> CONFIG_RUST=y
> CONFIG_RUSTC_VERSION_TEXT="rustc 1.81.0"
> CONFIG_HAVE_RUST=y
> CONFIG_RUST_FW_LOADER_ABSTRACTIONS=y
> CONFIG_BLK_DEV_RUST_NULL=m
> CONFIG_RADIO_TRUST=m
> CONFIG_HID_THRUSTMASTER=m
> CONFIG_THRUSTMASTER_FF=y
> CONFIG_TRUSTED_KEYS=m
> CONFIG_HAVE_TRUSTED_KEYS=y
> CONFIG_TRUSTED_KEYS_TPM=y
> CONFIG_TRUSTED_KEYS_TEE=y
> CONFIG_TRUSTED_KEYS_CAAM=y
> CONFIG_INTEGRITY_TRUSTED_KEYRING=y
> CONFIG_IMA_SECURE_AND_OR_TRUSTED_BOOT=y
> CONFIG_SYSTEM_TRUSTED_KEYRING=y
> CONFIG_SYSTEM_TRUSTED_KEYS=""
> CONFIG_SECONDARY_TRUSTED_KEYRING=y
> CONFIG_SECONDARY_TRUSTED_KEYRING_SIGNED_BY_BUILTIN=y
> CONFIG_SAMPLES_RUST=y
> CONFIG_SAMPLE_RUST_MINIMAL=m
> CONFIG_SAMPLE_RUST_PRINT=m
> CONFIG_SAMPLE_RUST_HOSTPROGS=y
> CONFIG_RUST_DEBUG_ASSERTIONS=y
> CONFIG_RUST_OVERFLOW_CHECKS=y
> CONFIG_RUST_BUILD_ASSERT_ALLOW=y
> 
> $ rustc --version
> rustc 1.81.0

Yeah, I'm not sure what's going on. I occasionally get rust stuff, but
mostly when I try allyesconfig. Weirdness.

> > Anyway, I think the above needs something like this:
> > 
> > ---
> > diff --git a/rust/helpers/spinlock.c b/rust/helpers/spinlock.c
> > index b7b0945e8b3c..5804a6062eb1 100644
> > --- a/rust/helpers/spinlock.c
> > +++ b/rust/helpers/spinlock.c
> > @@ -5,11 +5,16 @@
> >  void rust_helper___spin_lock_init(spinlock_t *lock, const char *name,
> >  				  struct lock_class_key *key)
> >  {
> > +#ifndef CONFIG_PREEMPT_RT
> >  #ifdef CONFIG_DEBUG_SPINLOCK
> >  	__raw_spin_lock_init(spinlock_check(lock), name, key, LD_WAIT_CONFIG);
> >  #else
> >  	spin_lock_init(lock);
> >  #endif
> > +#else
> > +	rt_mutex_base_init(&lock->lock);
> > +	__rt_spin_lock_init(lock, name, key, false);
> > +#endif
> >  }
> >  
> >  void rust_helper_spin_lock(spinlock_t *lock)
> 
> I will try to remember to add that to the tip tree merge tomorrow.

Boqun, could you test the above and make it happen?

> > > Without the revert CONFIG_PREEMPT_RT=y, after the revert it is not set
> > > and spinlock_check is only defined for !defined(CONFIG_PREEMPT_RT).  
> > 
> > Right, that moved PREEMPT_RT out of the preemption choice. Now I'm not
> > sure we want it =y for all{yes,mod}config. Is the below the right
> > incantation to avoid this?
> > 
> > ---
> > diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt
> > index 7c1b29a3a491..54ea59ff8fbe 100644
> > --- a/kernel/Kconfig.preempt
> > +++ b/kernel/Kconfig.preempt
> > @@ -88,7 +88,7 @@ endchoice
> >  
> >  config PREEMPT_RT
> >  	bool "Fully Preemptible Kernel (Real-Time)"
> > -	depends on EXPERT && ARCH_SUPPORTS_RT
> > +	depends on EXPERT && ARCH_SUPPORTS_RT && !COMPILE_TEST
> >  	select PREEMPTION
> >  	help
> >  	  This option turns the kernel into a real-time kernel by replacing
> 
> Yeah, that will do it.

OK, I'll write it up and stick that in tip/sched/core along with them
patches that's causing the grief :-)