The exynos5_i2c_message_start enables interrupts while holding the i2c
lock which is sought by the irq handler. If an IRQ is received before
this lock is released then a deadlock occurs.
This is only seen on an RT patched kernel, due to the transformation of
spinlocks into sleeping locks. By using raw_spinlocks here the same code
can run in mainline or an RT patched kernel. No change for !RT kenrels
[ 10.992238] kernel BUG at ../kernel/locking/rtmutex.c:998!
[ 10.992243] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
[ 10.992250] Modules linked in:
[ 10.992258] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.1.5-rt5
[ 10.992263] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
[ 10.992268] task: ed880000 ti: ed888000 task.ti: ed888000
[ 10.992281] PC is at rt_spin_lock_slowlock+0xa4/0x2ec
[ 10.992288] LR is at rt_spin_lock_slowlock+0x54/0x2ec
[ 10.992296] pc : [<c099e1bc>] lr : [<c099e16c>] psr: 60000193
[ 10.992296] sp : ed889a28 ip : ed880001 fp : 00000089
[ 10.992300] r10: ed889a28 r9 : c0f55654 r8 : 00000060
[ 10.992305] r7 : ed880000 r6 : 00000000 r5 : 00000001 r4 : ed9f7288
[ 10.992310] r3 : ed880000 r2 : 00000000 r1 : ed880000 r0 : 00000000
[ 10.992316] Flags: nZCv IRQs off FIQs on Mode SVC_32 ISA ARM
Segment kernel
...
...
[ 10.992662] [<c099e1bc>] (rt_spin_lock_slowlock) from [<c07bc794>]
(exynos5_i2c_irq+0x20/0x2b0)
[ 10.992678] [<c07bc794>] (exynos5_i2c_irq) from [<c028c8b4>]
(handle_irq_event_percpu+0x68/0x158)
[ 10.992690] [<c028c8b4>] (handle_irq_event_percpu) from [<c028ca0c>]
(handle_irq_event+0x68/0xa8)
[ 10.992702] [<c028ca0c>] (handle_irq_event) from [<c028f9c4>]
(handle_fasteoi_irq+0x11c/0x1d4)
[ 10.992713] [<c028f9c4>] (handle_fasteoi_irq) from [<c028c17c>]
(generic_handle_irq+0x20/0x30)
[ 10.992724] [<c028c17c>] (generic_handle_irq) from [<c028c290>]
(__handle_domain_irq+0x6c/0xe4)
[ 10.992734] [<c028c290>] (__handle_domain_irq) from [<c020a71c>]
(gic_handle_irq+0x2c/0x68)
[ 10.992744] [<c020a71c>] (gic_handle_irq) from [<c0214140>]
(__irq_svc+0x40/0x88)
[ 10.992749] Exception stack(0xed889b28 to 0xed889b70)
...
...
Signed-off-by: Anders Roxell <[email protected]>
---
drivers/i2c/busses/i2c-exynos5.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/drivers/i2c/busses/i2c-exynos5.c b/drivers/i2c/busses/i2c-exynos5.c
index b29c750..b12e77e 100644
--- a/drivers/i2c/busses/i2c-exynos5.c
+++ b/drivers/i2c/busses/i2c-exynos5.c
@@ -170,7 +170,7 @@ struct exynos5_i2c {
struct device *dev;
int state;
- spinlock_t lock; /* IRQ synchronization */
+ raw_spinlock_t lock; /* IRQ synchronization */
/*
* Since the TRANS_DONE bit is cleared on read, and we may read it
@@ -433,7 +433,7 @@ static irqreturn_t exynos5_i2c_irq(int irqno, void *dev_id)
i2c->state = -EINVAL;
- spin_lock(&i2c->lock);
+ raw_spin_lock(&i2c->lock);
int_status = readl(i2c->regs + HSI2C_INT_STATUS);
writel(int_status, i2c->regs + HSI2C_INT_STATUS);
@@ -521,7 +521,7 @@ static irqreturn_t exynos5_i2c_irq(int irqno, void *dev_id)
complete(&i2c->msg_complete);
}
- spin_unlock(&i2c->lock);
+ raw_spin_unlock(&i2c->lock);
return IRQ_HANDLED;
}
@@ -610,7 +610,7 @@ static void exynos5_i2c_message_start(struct exynos5_i2c *i2c, int stop)
* Enable interrupts before starting the transfer so that we don't
* miss any INT_I2C interrupts.
*/
- spin_lock_irqsave(&i2c->lock, flags);
+ raw_spin_lock_irqsave(&i2c->lock, flags);
writel(int_en, i2c->regs + HSI2C_INT_ENABLE);
if (stop == 1)
@@ -618,7 +618,7 @@ static void exynos5_i2c_message_start(struct exynos5_i2c *i2c, int stop)
i2c_auto_conf |= i2c->msg->len;
i2c_auto_conf |= HSI2C_MASTER_RUN;
writel(i2c_auto_conf, i2c->regs + HSI2C_AUTO_CONF);
- spin_unlock_irqrestore(&i2c->lock, flags);
+ raw_spin_unlock_irqrestore(&i2c->lock, flags);
}
static int exynos5_i2c_xfer_msg(struct exynos5_i2c *i2c,
@@ -763,7 +763,7 @@ static int exynos5_i2c_probe(struct platform_device *pdev)
/* Clear pending interrupts from u-boot or misc causes */
exynos5_i2c_clr_pend_irq(i2c);
- spin_lock_init(&i2c->lock);
+ raw_spin_lock_init(&i2c->lock);
init_completion(&i2c->msg_complete);
i2c->irq = ret = platform_get_irq(pdev, 0);
--
2.1.4
On Tue, 25 Aug 2015, Anders Roxell wrote:
> The exynos5_i2c_message_start enables interrupts while holding the i2c
> lock which is sought by the irq handler. If an IRQ is received before
> this lock is released then a deadlock occurs.
That's crap. The interrupt handler runs in an irq thread as RT forces
all normal interrupts to that.
Thanks,
tglx
On 2015-08-25 23:51, Thomas Gleixner wrote:
> On Tue, 25 Aug 2015, Anders Roxell wrote:
>
> > The exynos5_i2c_message_start enables interrupts while holding the i2c
> > lock which is sought by the irq handler. If an IRQ is received before
> > this lock is released then a deadlock occurs.
>
> That's crap. The interrupt handler runs in an irq thread as RT forces
> all normal interrupts to that.
You are right, I will send a v2 with a better changelog.
Cheers,
Anders