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Subject[PATCH v1 0/2] arm64: run softirqs on the per-CPU IRQ stack
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Hi all,

Currently arm64 supports per-CPU IRQ stack, but softirqs are
still handled in the task context.

Since any call to local_bh_enable() at any level in the task's
call stack may trigger a softirq processing run, which could
potentially cause a task stack overflow if the combined stack
footprints exceed the stack's size. And we did encounter this
situation in the real environment:

Call trace:
dump_backtrace+0x0/0x1cc,
show_stack+0x14/0x1c,
dump_stack+0xc4/0xfc,
panic+0x150/0x2c8,
panic+0x0/0x2c8,
handle_bad_stack+0x11c/0x130,
__bad_stack+0x88/0x8c,
vsnprintf+0x2c/0x524,
vscnprintf+0x38/0x7c,
scnprintf+0x6c/0x90,
/* ... */
__do_softirq+0x1e0/0x370,
do_softirq+0x40/0x50,
__local_bh_enable_ip+0x8c/0x90,
_raw_spin_unlock_bh+0x1c/0x24,
/* ... */
process_one_work+0x1dc/0x3e4,
worker_thread+0x260/0x360,
kthread+0x118/0x128,
ret_from_fork+0x10/0x18,

So let's run these softirqs on the IRQ stack as well.

This series is based on next-20220707.

Comments and suggestions are welcome.

Thanks,
Qi

RFC: https://lore.kernel.org/lkml/20220707110511.52129-1-zhengqi.arch@bytedance.com/

Changelog in RFC -> v1:
- fix conflicts with commit f2c5092190f2 ("arch/*: Disable softirq stacks on PREEMPT_RT.")

Qi Zheng (2):
arm64: run softirqs on the per-CPU IRQ stack
arm64: support HAVE_IRQ_EXIT_ON_IRQ_STACK

arch/arm64/Kconfig | 2 ++
arch/arm64/include/asm/exception.h | 4 +++-
arch/arm64/kernel/entry-common.c | 30 ++++++++++++++++++++----------
arch/arm64/kernel/entry.S | 6 ++++--
arch/arm64/kernel/irq.c | 14 ++++++++++++++
5 files changed, 43 insertions(+), 13 deletions(-)

--
2.20.1

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