Re: [Intel-gfx] [PATCH] rtc: cmos: Don't enable interrupts in the middle of the interrupt handler

[Chris Wilson]

On Wed, Oct 19, 2016 at 09:02:04PM +0300, ville.syrjala@xxxxxxxxxxxxxxx wrote:
> From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> 
> Using spin_lock_irq()/spin_unlock_irq() from within the interrupt
> handler is a no-no. Let's save/restore the flags to avoid turning on
> interrupts prematurely.
> 
> We hit this in a bunch of our CI systems, but for whatever reason I
> wasn't able to reproduce on my own machine, so this fix is just
> based on the backtrace.
> 
> [  202.634918] WARNING: CPU: 0 PID: 0 at kernel/locking/lockdep.c:2729 trace_hardirqs_on_caller+0x113/0x1b0
> [  202.634919] DEBUG_LOCKS_WARN_ON(current->hardirq_context)
> [  202.634929] Modules linked in: snd_hda_intel i915 x86_pkg_temp_thermal intel_powerclamp coretemp crct10dif_pclmul crc32_pclmul ghash_clmulni_intel lpc_ich snd_hda_codec_realtek snd_hda_codec_generic snd_hda_codec_hdmi snd_hda_codec snd_hwdep i2c_designware_platform i2c_designware_core snd_hda_core mei_me mei snd_pcm r8169 mii sdhci_acpi sdhci mmc_core i2c_hid [last unloaded: i915]
> [  202.634930] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G     U          4.9.0-rc1-CI-CI_DRM_1734+ #1
> [  202.634931] Hardware name: GIGABYTE M4HM87P-00/M4HM87P-00, BIOS F6 12/10/2014
> [  202.634933]  ffff88011ea03d68 ffffffff8142dce5 ffff88011ea03db8 0000000000000000
> [  202.634934]  ffff88011ea03da8 ffffffff8107e496 00000aa900000002 ffffffff81e249a0
> [  202.634935]  ffffffff81815637 ffffffff82e7c280 0000000000000000 0000000000000004
> [  202.634936] Call Trace:
> [  202.634939]  <IRQ>
> [  202.634939]  [<ffffffff8142dce5>] dump_stack+0x67/0x92
> [  202.634941]  [<ffffffff8107e496>] __warn+0xc6/0xe0
> [  202.634944]  [<ffffffff81815637>] ? _raw_spin_unlock_irq+0x27/0x50
> [  202.634945]  [<ffffffff8107e4fa>] warn_slowpath_fmt+0x4a/0x50
> [  202.634946]  [<ffffffff810d6d83>] trace_hardirqs_on_caller+0x113/0x1b0
> [  202.634948]  [<ffffffff810d6e2d>] trace_hardirqs_on+0xd/0x10
> [  202.634949]  [<ffffffff81815637>] _raw_spin_unlock_irq+0x27/0x50
> [  202.634951]  [<ffffffff81672042>] rtc_handler+0x32/0xa0
> [  202.634954]  [<ffffffff814c08a3>] acpi_ev_fixed_event_detect+0xd4/0xfb
> [  202.634956]  [<ffffffff814c2ccb>] acpi_ev_sci_xrupt_handler+0xf/0x2d
> [  202.634957]  [<ffffffff814ab3ee>] acpi_irq+0x11/0x2c
> [  202.634960]  [<ffffffff810e5288>] __handle_irq_event_percpu+0x58/0x370
> [  202.634961]  [<ffffffff810e55be>] handle_irq_event_percpu+0x1e/0x50
> [  202.634962]  [<ffffffff810e5624>] handle_irq_event+0x34/0x60
> [  202.634963]  [<ffffffff810e8906>] handle_fasteoi_irq+0xa6/0x170
> [  202.634966]  [<ffffffff8101eef5>] handle_irq+0x15/0x20
> [  202.634967]  [<ffffffff8101e548>] do_IRQ+0x68/0x130
> [  202.634968]  [<ffffffff81816789>] common_interrupt+0x89/0x89
> [  202.634970]  <EOI>
> [  202.634970]  [<ffffffff81814c73>] ? mwait_idle+0x93/0x210
> [  202.634971]  [<ffffffff81814c6a>] ? mwait_idle+0x8a/0x210
> [  202.634972]  [<ffffffff81026b0a>] arch_cpu_idle+0xa/0x10
> [  202.634973]  [<ffffffff8181509e>] default_idle_call+0x1e/0x30
> [  202.634974]  [<ffffffff810cbf6c>] cpu_startup_entry+0x17c/0x1f0
> [  202.634976]  [<ffffffff8180ca87>] rest_init+0x127/0x130
> [  202.634978]  [<ffffffff81f77f08>] start_kernel+0x3f6/0x403
> [  202.634980]  [<ffffffff81f7728f>] x86_64_start_reservations+0x2a/0x2c
> [  202.634981]  [<ffffffff81f77404>] x86_64_start_kernel+0x173/0x186
> [  202.634982] ---[ end trace 293c99618fa08d34 ]---
> 
> Cc: Gabriele Mazzotta <gabriele.mzt@xxxxxxxxx>
> Cc: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx>
> Fixes: 983bf1256edb ("rtc: cmos: Clear ACPI-driven alarms upon resume")
> Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> ---
>  drivers/rtc/rtc-cmos.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
> index dd3d59806ffa..19cd49ad92dc 100644
> --- a/drivers/rtc/rtc-cmos.c
> +++ b/drivers/rtc/rtc-cmos.c
> @@ -996,8 +996,9 @@ static u32 rtc_handler(void *context)
>  	struct cmos_rtc *cmos = dev_get_drvdata(dev);
>  	unsigned char rtc_control = 0;
>  	unsigned char rtc_intr;
> +	unsigned long flags;
>  
> -	spin_lock_irq(&rtc_lock);
> +	spin_lock_irqsave(&rtc_lock, flags);

My reading of the acpi fixed event handlers suggests that this can only
be called from interrupt context.

Anyway using irqsave is correct (just may be optimised away to a plain
spin_lock() if the condition that this is only called in irq context is
satisfied).

Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre