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author | Guilherme G. Piccoli <gpiccoli@igalia.com> | 2022-08-19 19:17:29 -0300 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-12-31 13:32:56 +0100 |
commit | 16fed31153ceeb7be73dd74370a7c09e77a84dfb (patch) | |
tree | 302e90cacccdda202c3bab27c029433093ef9eef /drivers/hv | |
parent | 2e356d6de4c71389c493adb444fd52333e72c2dc (diff) | |
download | linux-16fed31153ceeb7be73dd74370a7c09e77a84dfb.tar.gz |
video: hyperv_fb: Avoid taking busy spinlock on panic path
[ Upstream commit 1d044ca035dc22df0d3b39e56f2881071d9118bd ] The Hyper-V framebuffer code registers a panic notifier in order to try updating its fbdev if the kernel crashed. The notifier callback is straightforward, but it calls the vmbus_sendpacket() routine eventually, and such function takes a spinlock for the ring buffer operations. Panic path runs in atomic context, with local interrupts and preemption disabled, and all secondary CPUs shutdown. That said, taking a spinlock might cause a lockup if a secondary CPU was disabled with such lock taken. Fix it here by checking if the ring buffer spinlock is busy on Hyper-V framebuffer panic notifier; if so, bail-out avoiding the potential lockup scenario. Cc: Andrea Parri (Microsoft) <parri.andrea@gmail.com> Cc: Dexuan Cui <decui@microsoft.com> Cc: Haiyang Zhang <haiyangz@microsoft.com> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Cc: Michael Kelley <mikelley@microsoft.com> Cc: Stephen Hemminger <sthemmin@microsoft.com> Cc: Tianyu Lan <Tianyu.Lan@microsoft.com> Cc: Wei Liu <wei.liu@kernel.org> Tested-by: Fabio A M Martins <fabiomirmar@gmail.com> Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com> Reviewed-by: Michael Kelley <mikelley@microsoft.com> Link: https://lore.kernel.org/r/20220819221731.480795-10-gpiccoli@igalia.com Signed-off-by: Wei Liu <wei.liu@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'drivers/hv')
-rw-r--r-- | drivers/hv/ring_buffer.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c index 59a4aa86d1f3..c6692fd5ab15 100644 --- a/drivers/hv/ring_buffer.c +++ b/drivers/hv/ring_buffer.c @@ -280,6 +280,19 @@ void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info) ring_info->pkt_buffer_size = 0; } +/* + * Check if the ring buffer spinlock is available to take or not; used on + * atomic contexts, like panic path (see the Hyper-V framebuffer driver). + */ + +bool hv_ringbuffer_spinlock_busy(struct vmbus_channel *channel) +{ + struct hv_ring_buffer_info *rinfo = &channel->outbound; + + return spin_is_locked(&rinfo->ring_lock); +} +EXPORT_SYMBOL_GPL(hv_ringbuffer_spinlock_busy); + /* Write to the ring buffer. */ int hv_ringbuffer_write(struct vmbus_channel *channel, const struct kvec *kv_list, u32 kv_count, |