Re: [PATCH] hwmon: xgene: Fix crash when alarm occurs before driver probe
From: Guenter Roeck
Date: Wed Sep 07 2016 - 02:40:21 EST
On 09/06/2016 11:07 PM, Hoan Tran wrote:
Hi Guenter,
On Tue, Sep 6, 2016 at 10:50 PM, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
On 09/06/2016 10:21 PM, Hoan Tran wrote:
Hi Guenter,
Thank for your quick review !
On Tue, Sep 6, 2016 at 9:35 PM, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
On 09/06/2016 08:46 PM, Hoan Tran wrote:
The system crashes during probing xgene-hwmon driver when temperature
alarm interrupt occurs before.
It's because
- xgene_hwmon_probe() requests PCC mailbox channel which also enables
the mailbox interrupt.
- As temperature alarm interrupt is pending, ISR runs and crashes when
accesses
into invalid resource as unmapped PCC shared memory.
This patch fixes this issue by saving this alarm message and scheduling
a
bottom handler after xgene_hwmon_probe() finish.
I am not completely happy with this fix. Main problem I have is that the
processing associated with resp_pending doesn't happen until init_flag is
set.
Since the hwmon functions can be called right after
hwmon_device_register_with_groups(),
there is now a new race condition between that call and setting
init_flag.
I think it's still good if hwmon functions are called right after
hwmon_device_register_with_groups().
The response message will be queued into FIFO and be processed later.
Yes, but the call to complete() won't happen in this case, or am I missing
something ?
Yes, I think xgene_hwmon_rd() and xgene_hwmon_pcc_rd() functions have
to check "init_flag == true" before issue the read command.
This is getting more and more messy :-(
Thanks
Hoan
Guenter
I am also a bit concerned with init_flag and rx_pending not being atomic
and
protected.
What happens if a second interrupt occurs right after init_flag is set
but
before
(or while) rx_pending is evaluated ?
Yah, that's a good catch. I can re-use the "kfifo_lock" spinlock for
this atomic protection.
On top of that, init_flag and thus the added complexity is (unless I am
missing
something) only needed if acpi is enabled. Penaltizing non-acpi code
doesn't
seem
to be optimal.
I think, with DT, we still need this flag. In a case of temperature
alarm, the driver needs to set "temp1_critical_alarm" sysfs.
This "temp1_critical_alarm" should be created before "init_flag" = true.
I don't know. After all, any such alarm would be lost if it occurred
before the driver was loaded, no ? Those mailboxes should really have
a means to be informed that the initiator is ready to handle
interrupts/callbacks.
Guenter
Thanks
Hoan
How do other drivers handle this situation ? This must be a common
problem
with all mbox users.
Thanks,
Guenter
Signed-off-by: Hoan Tran <hotran@xxxxxxx>
Reported-by: Itaru Kitayama <itaru.kitayama@xxxxxxxx>
---
drivers/hwmon/xgene-hwmon.c | 75
+++++++++++++++++++++++++++++++++------------
1 file changed, 56 insertions(+), 19 deletions(-)
diff --git a/drivers/hwmon/xgene-hwmon.c b/drivers/hwmon/xgene-hwmon.c
index bc78a5d..e3b4e84 100644
--- a/drivers/hwmon/xgene-hwmon.c
+++ b/drivers/hwmon/xgene-hwmon.c
@@ -107,6 +107,8 @@ struct xgene_hwmon_dev {
struct completion rd_complete;
int resp_pending;
struct slimpro_resp_msg sync_msg;
+ bool init_flag;
+ bool rx_pending;
struct work_struct workq;
struct kfifo_rec_ptr_1 async_msg_fifo;
@@ -465,13 +467,35 @@ static void xgene_hwmon_evt_work(struct
work_struct
*work)
}
}
+static int xgene_hwmon_rx_ready(struct xgene_hwmon_dev *ctx, void *msg)
+{
+ if (!ctx->init_flag) {
+ ctx->rx_pending = true;
+ /* Enqueue to the FIFO */
+ kfifo_in_spinlocked(&ctx->async_msg_fifo, msg,
+ sizeof(struct slimpro_resp_msg),
+ &ctx->kfifo_lock);
+ return -EBUSY;
+ }
+
+ return 0;
+}
+
/*
* This function is called when the SLIMpro Mailbox received a message
*/
static void xgene_hwmon_rx_cb(struct mbox_client *cl, void *msg)
{
struct xgene_hwmon_dev *ctx = to_xgene_hwmon_dev(cl);
- struct slimpro_resp_msg amsg;
+
+ /*
+ * While the driver registers with the mailbox framework, an
interrupt
+ * can be pending before the probe function completes its
+ * initialization. If such condition occurs, just queue up the
message
+ * as the driver is not ready for servicing the callback.
+ */
+ if (xgene_hwmon_rx_ready(ctx, msg) < 0)
+ return;
/*
* Response message format:
@@ -500,12 +524,8 @@ static void xgene_hwmon_rx_cb(struct mbox_client
*cl,
void *msg)
return;
}
- amsg.msg = ((u32 *)msg)[0];
- amsg.param1 = ((u32 *)msg)[1];
- amsg.param2 = ((u32 *)msg)[2];
-
/* Enqueue to the FIFO */
- kfifo_in_spinlocked(&ctx->async_msg_fifo, &amsg,
+ kfifo_in_spinlocked(&ctx->async_msg_fifo, msg,
sizeof(struct slimpro_resp_msg),
&ctx->kfifo_lock);
/* Schedule the bottom handler */
schedule_work(&ctx->workq);
@@ -520,6 +540,15 @@ static void xgene_hwmon_pcc_rx_cb(struct
mbox_client
*cl, void *msg)
struct acpi_pcct_shared_memory *generic_comm_base =
ctx->pcc_comm_addr;
struct slimpro_resp_msg amsg;
+ /*
+ * While the driver registers with the mailbox framework, an
interrupt
+ * can be pending before the probe function completes its
+ * initialization. If such condition occurs, just queue up the
message
+ * as the driver is not ready for servicing the callback.
+ */
+ if (xgene_hwmon_rx_ready(ctx, &amsg) < 0)
+ return;
+
msg = generic_comm_base + 1;
/* Check if platform sends interrupt */
if (!xgene_word_tst_and_clr(&generic_comm_base->status,
@@ -596,6 +625,17 @@ static int xgene_hwmon_probe(struct platform_device
*pdev)
platform_set_drvdata(pdev, ctx);
cl = &ctx->mbox_client;
+ spin_lock_init(&ctx->kfifo_lock);
+ mutex_init(&ctx->rd_mutex);
+
+ rc = kfifo_alloc(&ctx->async_msg_fifo,
+ sizeof(struct slimpro_resp_msg) *
ASYNC_MSG_FIFO_SIZE,
+ GFP_KERNEL);
+ if (rc)
+ goto out_mbox_free;
+
+ INIT_WORK(&ctx->workq, xgene_hwmon_evt_work);
+
/* Request mailbox channel */
cl->dev = &pdev->dev;
cl->tx_done = xgene_hwmon_tx_done;
@@ -676,17 +716,6 @@ static int xgene_hwmon_probe(struct platform_device
*pdev)
ctx->usecs_lat = PCC_NUM_RETRIES * cppc_ss->latency;
}
- spin_lock_init(&ctx->kfifo_lock);
- mutex_init(&ctx->rd_mutex);
-
- rc = kfifo_alloc(&ctx->async_msg_fifo,
- sizeof(struct slimpro_resp_msg) *
ASYNC_MSG_FIFO_SIZE,
- GFP_KERNEL);
- if (rc)
- goto out_mbox_free;
-
- INIT_WORK(&ctx->workq, xgene_hwmon_evt_work);
-
ctx->hwmon_dev = hwmon_device_register_with_groups(ctx->dev,
"apm_xgene",
ctx,
@@ -697,17 +726,25 @@ static int xgene_hwmon_probe(struct
platform_device
*pdev)
goto out;
}
+ ctx->init_flag = true;
+ if (ctx->rx_pending) {
+ /*
+ * If there is a pending message, schedule the bottom
handler
+ */
+ schedule_work(&ctx->workq);
+ }
+
dev_info(&pdev->dev, "APM X-Gene SoC HW monitor driver
registered\n");
return 0;
out:
- kfifo_free(&ctx->async_msg_fifo);
-out_mbox_free:
if (acpi_disabled)
mbox_free_channel(ctx->mbox_chan);
else
pcc_mbox_free_channel(ctx->mbox_chan);
+out_mbox_free:
+ kfifo_free(&ctx->async_msg_fifo);
return rc;
}