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

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?

Will