[PATCH] mmc: host: meson-gx-mmc: fix possible deadlock condition for preempt_rt

[Brad Harper]

Force threaded interrupts for meson_mmc_irq to prevent possible deadlock 
condition
during mmc operations when using preempt_rt with 5.9.0-rc3-rt3 patches 
on arm64.

Using meson-gx-mmc with an emmc device on Hardkernel Odroid N2+ 
configured with
preempt_rt resulted in the soc becoming unresponsive.  With lock 
checking enabled
the below inconsistent lock state was observed during boot.

After some discussions with tglx in IRC #linux-rt the attached patch was 
suggested
to remove IRQF_ONESHOT from request_threaded_irq.
This has been tested and confirmed by me to resolve both the 
unresponsive soc and
the inconsistent lock state warning when using 5.9.0-rc3-rt3 on arm64 
Odroid N2+.

Further review and testing is required to ensure there are no adverse 
impacts or
concerns and that is the correct method to resolve the problem.  I will 
continue
to test on various amlogic devices with both standard mainline low 
latency kernel
and preempt_rt kernel with -rt patches.

[ 7.858446] ================================
[ 7.858448] WARNING: inconsistent lock state
[ 7.858450] 5.9.0-rc3-rt3+ #33 Not tainted
[ 7.858453] --------------------------------
[ 7.858456] inconsistent {IN-HARDIRQ-R} -> {HARDIRQ-ON-W} usage.
[ 7.858459] swapper/0/1 [HC0[0]:SC0[0]:HE1:SE1] takes:
[ 7.858465] ffff80001219f4d8 (&trig->leddev_list_lock){+?.+}-{0:0}, at: 
led_trigger_set+0x104/0x270
[ 7.858482] {IN-HARDIRQ-R} state was registered at:
[ 7.858484] lock_acquire+0xec/0x468
[ 7.858491] rt_read_lock+0xb0/0x108
[ 7.858497] led_trigger_event+0x34/0x88
[ 7.858501] mmc_request_done+0x3f0/0x450
[ 7.858505] meson_mmc_irq+0x284/0x378
[ 7.858511] __handle_irq_event_percpu+0xcc/0x4a8
[ 7.858515] handle_irq_event_percpu+0x60/0xb0
[ 7.858519] handle_irq_event+0x50/0x108
[ 7.858522] handle_fasteoi_irq+0xd0/0x180
[ 7.858527] generic_handle_irq+0x38/0x50
[ 7.858530] __handle_domain_irq+0x6c/0xc8
[ 7.858533] gic_handle_irq+0x5c/0xb8
[ 7.858537] el1_irq+0xbc/0x180
[ 7.858540] arch_cpu_idle+0x28/0x38
[ 7.858544] default_idle_call+0x90/0x3f0
[ 7.858547] do_idle+0x250/0x268
[ 7.858551] cpu_startup_entry+0x2c/0x78
[ 7.858554] rest_init+0x1b0/0x284
[ 7.858559] arch_call_rest_init+0x18/0x24
[ 7.858565] start_kernel+0x550/0x588
[ 7.858569] irq event stamp: 1925495
[ 7.858571] hardirqs last enabled at (1925495): [<ffff8000111e3ba4>] 
_raw_spin_unlock_irqrestore+0xa4/0xb0
[ 7.858576] hardirqs last disabled at (1925494): [<ffff8000111e3c58>] 
_raw_spin_lock_irqsave+0xa8/0xb8
[ 7.858580] softirqs last enabled at (1857856): [<ffff80001024705c>] 
bdi_register_va+0x114/0x368
[ 7.858586] softirqs last disabled at (1857849): [<ffff80001024705c>] 
bdi_register_va+0x114/0x368
[ 7.858590]
other info that might help us debug this:
[ 7.858592] Possible unsafe locking scenario:
[ 7.858594] CPU0
[ 7.858595] ----
[ 7.858597] lock(&trig->leddev_list_lock);
[ 7.858600] <Interrupt>
[ 7.858602] lock(&trig->leddev_list_lock);
[ 7.858604]
*** DEADLOCK ***
[ 7.858606] 3 locks held by swapper/0/1:
[ 7.858609] #0: ffff80001219eb30 (leds_list_lock){++++}-{0:0}, at: 
led_trigger_register+0xf4/0x1c0
[ 7.858619] #1: ffff0000b0696a70 (&led_cdev->trigger_lock){+.+.}-{0:0}, 
at: led_trigger_register+0x134/0x1c0
[ 7.858629] #2: ffff800011fb83d0 (rcu_read_lock){....}-{1:2}, at: 
rt_write_lock+0x8/0x108
[ 7.858637]
stack backtrace:
[ 7.858640] CPU: 5 PID: 1 Comm: swapper/0 Not tainted 5.9.0-rc3-rt3+ #33
[ 7.858643] Hardware name: Hardkernel ODROID-N2Plus (DT)
[ 7.858646] Call trace:
[ 7.858647] dump_backtrace+0x0/0x1e8
[ 7.858650] show_stack+0x20/0x30
[ 7.858653] dump_stack+0xf0/0x164
[ 7.858659] print_usage_bug+0x2b4/0x2c0
[ 7.858662] mark_lock+0x2e8/0x360
[ 7.858665] __lock_acquire+0x238/0x1858
[ 7.858669] lock_acquire+0xec/0x468
[ 7.858672] rt_write_lock+0xb0/0x108
[ 7.858675] led_trigger_set+0x104/0x270
[ 7.858678] led_trigger_register+0x180/0x1c0
[ 7.858681] heartbeat_trig_init+0x28/0x5c
[ 7.858686] do_one_initcall+0x90/0x4bc
[ 7.858690] kernel_init_freeable+0x2cc/0x338
[ 7.858694] kernel_init+0x1c/0x11c
[ 7.858697] ret_from_fork+0x10/0x34

Signed-off-by: Brad Harper <bjharper@xxxxxxxxx>
---
 drivers/mmc/host/meson-gx-mmc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mmc/host/meson-gx-mmc.c 
b/drivers/mmc/host/meson-gx-mmc.c
index 08a3b1c05..130ac134d 100644
--- a/drivers/mmc/host/meson-gx-mmc.c
+++ b/drivers/mmc/host/meson-gx-mmc.c
@@ -1139,7 +1139,7 @@ static int meson_mmc_probe(struct platform_device 
*pdev)
               host->regs + SD_EMMC_IRQ_EN);

        ret = request_threaded_irq(host->irq, meson_mmc_irq,
-                                  meson_mmc_irq_thread, IRQF_ONESHOT,
+                                  meson_mmc_irq_thread, 0,
                                   dev_name(&pdev->dev), host);
        if (ret)
                goto err_init_clk;
--
2.20.1