* [PATCH v4] dmaengine: idxd: Convert spinlock to mutex to lock evl workqueue
@ 2024-04-04 22:39 Fenghua Yu
2024-04-07 16:38 ` Vinod Koul
0 siblings, 1 reply; 2+ messages in thread
From: Fenghua Yu @ 2024-04-04 22:39 UTC (permalink / raw
To: Vinod Koul, Dave Jiang
Cc: dmaengine, linux-kernel, Rex Zhang, Fenghua Yu, Lijun Pan
From: Rex Zhang <rex.zhang@intel.com>
drain_workqueue() cannot be called safely in a spinlocked context due to
possible task rescheduling. In the multi-task scenario, calling
queue_work() while drain_workqueue() will lead to a Call Trace as
pushing a work on a draining workqueue is not permitted in spinlocked
context.
Call Trace:
<TASK>
? __warn+0x7d/0x140
? __queue_work+0x2b2/0x440
? report_bug+0x1f8/0x200
? handle_bug+0x3c/0x70
? exc_invalid_op+0x18/0x70
? asm_exc_invalid_op+0x1a/0x20
? __queue_work+0x2b2/0x440
queue_work_on+0x28/0x30
idxd_misc_thread+0x303/0x5a0 [idxd]
? __schedule+0x369/0xb40
? __pfx_irq_thread_fn+0x10/0x10
? irq_thread+0xbc/0x1b0
irq_thread_fn+0x21/0x70
irq_thread+0x102/0x1b0
? preempt_count_add+0x74/0xa0
? __pfx_irq_thread_dtor+0x10/0x10
? __pfx_irq_thread+0x10/0x10
kthread+0x103/0x140
? __pfx_kthread+0x10/0x10
ret_from_fork+0x31/0x50
? __pfx_kthread+0x10/0x10
ret_from_fork_asm+0x1b/0x30
</TASK>
The current implementation uses a spinlock to protect event log workqueue
and will lead to the Call Trace due to potential task rescheduling.
To address the locking issue, convert the spinlock to mutex, allowing
the drain_workqueue() to be called in a safe mutex-locked context.
This change ensures proper synchronization when accessing the event log
workqueue, preventing potential Call Trace and improving the overall
robustness of the code.
Fixes: c40bd7d9737b ("dmaengine: idxd: process user page faults for completion record")
Signed-off-by: Rex Zhang <rex.zhang@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Fenghua Yu <fenghua.yu@intel.com>
Reviewed-by: Lijun Pan <lijun.pan@intel.com>
---
Changlog:
v4:
- No functional changes. This patch was not picked up before. So rebase
the patch to the latest kernel version and resend it.
- Update the commit message to provide more details on the issue and
the fix.
- Fenghua Yu sends the patch to the dmaengine/lkml mailing lists.
v3:
https://lore.kernel.org/dmaengine/20240123034831.3020048-1-rex.zhang@intel.com/
drivers/dma/idxd/cdev.c | 5 ++---
drivers/dma/idxd/debugfs.c | 4 ++--
drivers/dma/idxd/device.c | 8 ++++----
drivers/dma/idxd/idxd.h | 2 +-
drivers/dma/idxd/init.c | 2 +-
drivers/dma/idxd/irq.c | 4 ++--
6 files changed, 12 insertions(+), 13 deletions(-)
diff --git a/drivers/dma/idxd/cdev.c b/drivers/dma/idxd/cdev.c
index 8078ab9acfbc..c095a2c8f659 100644
--- a/drivers/dma/idxd/cdev.c
+++ b/drivers/dma/idxd/cdev.c
@@ -342,7 +342,7 @@ static void idxd_cdev_evl_drain_pasid(struct idxd_wq *wq, u32 pasid)
if (!evl)
return;
- spin_lock(&evl->lock);
+ mutex_lock(&evl->lock);
status.bits = ioread64(idxd->reg_base + IDXD_EVLSTATUS_OFFSET);
t = status.tail;
h = status.head;
@@ -354,9 +354,8 @@ static void idxd_cdev_evl_drain_pasid(struct idxd_wq *wq, u32 pasid)
set_bit(h, evl->bmap);
h = (h + 1) % size;
}
- spin_unlock(&evl->lock);
-
drain_workqueue(wq->wq);
+ mutex_unlock(&evl->lock);
}
static int idxd_cdev_release(struct inode *node, struct file *filep)
diff --git a/drivers/dma/idxd/debugfs.c b/drivers/dma/idxd/debugfs.c
index f3f25ee676f3..ad4245cb301d 100644
--- a/drivers/dma/idxd/debugfs.c
+++ b/drivers/dma/idxd/debugfs.c
@@ -66,7 +66,7 @@ static int debugfs_evl_show(struct seq_file *s, void *d)
if (!evl || !evl->log)
return 0;
- spin_lock(&evl->lock);
+ mutex_lock(&evl->lock);
evl_status.bits = ioread64(idxd->reg_base + IDXD_EVLSTATUS_OFFSET);
t = evl_status.tail;
@@ -87,7 +87,7 @@ static int debugfs_evl_show(struct seq_file *s, void *d)
dump_event_entry(idxd, s, i, &count, processed);
}
- spin_unlock(&evl->lock);
+ mutex_unlock(&evl->lock);
return 0;
}
diff --git a/drivers/dma/idxd/device.c b/drivers/dma/idxd/device.c
index ecfdf4a8f1f8..c41ef195eeb9 100644
--- a/drivers/dma/idxd/device.c
+++ b/drivers/dma/idxd/device.c
@@ -775,7 +775,7 @@ static int idxd_device_evl_setup(struct idxd_device *idxd)
goto err_alloc;
}
- spin_lock(&evl->lock);
+ mutex_lock(&evl->lock);
evl->log = addr;
evl->dma = dma_addr;
evl->log_size = size;
@@ -796,7 +796,7 @@ static int idxd_device_evl_setup(struct idxd_device *idxd)
gencfg.evl_en = 1;
iowrite32(gencfg.bits, idxd->reg_base + IDXD_GENCFG_OFFSET);
- spin_unlock(&evl->lock);
+ mutex_unlock(&evl->lock);
return 0;
err_alloc:
@@ -819,7 +819,7 @@ static void idxd_device_evl_free(struct idxd_device *idxd)
if (!gencfg.evl_en)
return;
- spin_lock(&evl->lock);
+ mutex_lock(&evl->lock);
gencfg.evl_en = 0;
iowrite32(gencfg.bits, idxd->reg_base + IDXD_GENCFG_OFFSET);
@@ -836,7 +836,7 @@ static void idxd_device_evl_free(struct idxd_device *idxd)
evl_dma = evl->dma;
evl->log = NULL;
evl->size = IDXD_EVL_SIZE_MIN;
- spin_unlock(&evl->lock);
+ mutex_unlock(&evl->lock);
dma_free_coherent(dev, evl_log_size, evl_log, evl_dma);
}
diff --git a/drivers/dma/idxd/idxd.h b/drivers/dma/idxd/idxd.h
index a4099a1e2340..7b98944135eb 100644
--- a/drivers/dma/idxd/idxd.h
+++ b/drivers/dma/idxd/idxd.h
@@ -293,7 +293,7 @@ struct idxd_driver_data {
struct idxd_evl {
/* Lock to protect event log access. */
- spinlock_t lock;
+ struct mutex lock;
void *log;
dma_addr_t dma;
/* Total size of event log = number of entries * entry size. */
diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
index 4954adc6bb60..264c4e47d7cc 100644
--- a/drivers/dma/idxd/init.c
+++ b/drivers/dma/idxd/init.c
@@ -354,7 +354,7 @@ static int idxd_init_evl(struct idxd_device *idxd)
if (!evl)
return -ENOMEM;
- spin_lock_init(&evl->lock);
+ mutex_init(&evl->lock);
evl->size = IDXD_EVL_SIZE_MIN;
idxd_name = dev_name(idxd_confdev(idxd));
diff --git a/drivers/dma/idxd/irq.c b/drivers/dma/idxd/irq.c
index 348aa21389a9..8dc029c86551 100644
--- a/drivers/dma/idxd/irq.c
+++ b/drivers/dma/idxd/irq.c
@@ -363,7 +363,7 @@ static void process_evl_entries(struct idxd_device *idxd)
evl_status.bits = 0;
evl_status.int_pending = 1;
- spin_lock(&evl->lock);
+ mutex_lock(&evl->lock);
/* Clear interrupt pending bit */
iowrite32(evl_status.bits_upper32,
idxd->reg_base + IDXD_EVLSTATUS_OFFSET + sizeof(u32));
@@ -380,7 +380,7 @@ static void process_evl_entries(struct idxd_device *idxd)
evl_status.head = h;
iowrite32(evl_status.bits_lower32, idxd->reg_base + IDXD_EVLSTATUS_OFFSET);
- spin_unlock(&evl->lock);
+ mutex_unlock(&evl->lock);
}
irqreturn_t idxd_misc_thread(int vec, void *data)
--
2.37.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v4] dmaengine: idxd: Convert spinlock to mutex to lock evl workqueue
2024-04-04 22:39 [PATCH v4] dmaengine: idxd: Convert spinlock to mutex to lock evl workqueue Fenghua Yu
@ 2024-04-07 16:38 ` Vinod Koul
0 siblings, 0 replies; 2+ messages in thread
From: Vinod Koul @ 2024-04-07 16:38 UTC (permalink / raw
To: Dave Jiang, Fenghua Yu; +Cc: dmaengine, linux-kernel, Rex Zhang, Lijun Pan
On Thu, 04 Apr 2024 15:39:49 -0700, Fenghua Yu wrote:
> drain_workqueue() cannot be called safely in a spinlocked context due to
> possible task rescheduling. In the multi-task scenario, calling
> queue_work() while drain_workqueue() will lead to a Call Trace as
> pushing a work on a draining workqueue is not permitted in spinlocked
> context.
> Call Trace:
> <TASK>
> ? __warn+0x7d/0x140
> ? __queue_work+0x2b2/0x440
> ? report_bug+0x1f8/0x200
> ? handle_bug+0x3c/0x70
> ? exc_invalid_op+0x18/0x70
> ? asm_exc_invalid_op+0x1a/0x20
> ? __queue_work+0x2b2/0x440
> queue_work_on+0x28/0x30
> idxd_misc_thread+0x303/0x5a0 [idxd]
> ? __schedule+0x369/0xb40
> ? __pfx_irq_thread_fn+0x10/0x10
> ? irq_thread+0xbc/0x1b0
> irq_thread_fn+0x21/0x70
> irq_thread+0x102/0x1b0
> ? preempt_count_add+0x74/0xa0
> ? __pfx_irq_thread_dtor+0x10/0x10
> ? __pfx_irq_thread+0x10/0x10
> kthread+0x103/0x140
> ? __pfx_kthread+0x10/0x10
> ret_from_fork+0x31/0x50
> ? __pfx_kthread+0x10/0x10
> ret_from_fork_asm+0x1b/0x30
> </TASK>
>
> [...]
Applied, thanks!
[1/1] dmaengine: idxd: Convert spinlock to mutex to lock evl workqueue
commit: d5638de827cff0fce77007e426ec0ffdedf68a44
Best regards,
--
~Vinod
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