Re: [PATCH] PM: hibernate: flush icache for restored pages from task context

On Thu, Aug 06, 2026 at 08:56:18AM +0800, Xiong Xin wrote:
> > On Mon, Aug 03, 2026 at 01:54:12PM +0800, Xiong Xin wrote:
> > > When resuming from hibernation with `hibernate=nocompress`, the kernel
> > > loads the image via load_image(), which submits read bios asynchronously
> > > and waits on them with hib_wait_io(). The bio completion callback
> > > hib_end_io() runs from the block IRQ/softirq path.
> > > 
> > > Commit f6cf0545ec69 ("PM / Hibernate: Call flush_icache_range() on pages
> > > restored in-place") added a flush_icache_range() call inside hib_end_io()
> > > (under clean_pages_on_read). On architectures such as ARM64,
> > > flush_icache_range() ends with kick_all_cpus_sync() -> smp_call_function()
> > > (wait=1), which contains:
> > > 
> > >      WARN_ON_ONCE(!in_task());
> > > 
> > > Because hib_end_io() executes in hardirq/softirq context, in_task() is
> > > always false there, and the WARN fires which happens while the resume
> > > task is asleep in hib_wait_io() and the CPU is idle, the warning log as
> > > follows:
> > 
> > Hmm, do we have any secondary CPUs online at this point? I wonder if
> > either smp_call_function() could push the WARN() down into the branch
> > where it knows it is going to call remotely or whether we could elide
> > the call to kick_all_cpus_sync() altogether in that case?
> 
> Thanks for the review.
> 
> Q1: Do we have any secondary CPUs online at this point?
> 
> Yes, the secondary CPUs are online, but they are all (almost) in the idle
> loop state. 

Ah, nevermind then. I don't think we can elide the cross-call in the
low-level code in that case. Sorry for the bad suggestion!

Will