[PATCH v2] ARM, ARM64, LONGARCH: Delay HW BP notification to task_work()

[Russell King]

On Thu, Sep 03, 2026 at 06:07:10PM +0200, Sebastian Andrzej Siewior wrote:
> On 2026-08-14 10:51:18 [+0200], To linux-arm-kernel at lists.infradead.org wrote:
> > Waiman, Luis, Ada reported that HW breakpoints on ARM64 trigger
> > "sleeping while atomic" warnings on PREEMPT_RT. The hardware event is
> > delivered with disabled interrupts and perf intrastrucure expects
> > disabled interrupts while the overflow callback is invoked.
> > 
> > The callback then sends a SIGTRAP signal for which it acquires
> > sighand_struct::siglock, a spinlock_t which becomes a sleeping lock and
> > must not be acquired in atomic context.
> > 
> > Delay the event callback until the return to userland.
> > Add perf_arch_hwbp_notify(), a generic perf callback which delayes the
> > actual callback invocation to task_work_add() callback. This callback
> > invokes the architecture defines callback arch_hwbp_send_sig().
> > This requires struct callback_head and the functions require
> > ARCH_NEED_PERF_HW_NOTIF to be defined.
> > 
> > This was reported against ARM64. ARM and LongARCH follow the same
> > pattern are also converted.
> > 
> > Reported-by: Luis Claudio R. Goncalves <lgoncalv at redhat.com>
> > Reported-by: Waiman Long <longman at redhat.com>
> > Closes: https://lore.kernel.org/all/aho0eqjMESuHxECr@redhat.com/
> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy at linutronix.de>
> 
> Did this get lost, should I repost it or is there something obviously
> wrong with it and nobody wanted to hurt my feelings by telling me?

What do you expect to happen with this? Which arch maintainer should
apply this patch that affects three different independently maintained
architectures?

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