irqchip/riscv-imsic: Clear interrupt move state during CPU offlining

irqchip/riscv-imsic: Clear interrupt move state during CPU offlining

Affinity changes of IMSIC interrupts have to be careful to not lose an
interrupt in the process. Each vector keeps track of an affinity change in
progress with two pointers in struct imsic_vector.

imsic_vector::move_prev points to the previous CPU target data and
imsic_vector::move_next to the designated new CPU target data.

imsic_vector::move_prev on the new CPU can only be cleared after the
previous CPU has cleared imsic_vector::move_next, which ususally happens in
__imsic_remote_sync().

In case of CPU hot-unplug __imsic_remote_sync() is not invoked because the
CPU is already marked offline. That means imsic_vector::move_prev becomes
stale until the CPU is onlined again.

The stale pointer prevents further affinity changes for the affected
interrupts.

Solve this by clearing the imsic_vector::move_prev pointers in the CPU
hotplug offline path.

[ tglx: Replace word salad in change log ]

Fixes: 0f67911e821c ("irqchip/riscv-imsic: Separate next and previous pointers in IMSIC vector")
Signed-off-by: Yong-Xuan Wang <yongxuan.wang@sifive.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260508-imsic-v2-1-e9f08dd46cf5@sifive.com