Am 06.05.20 um 05:45 schrieb Zhao, Jiange:
[AMD Official Use Only - Internal Distribution Only]
Hi Christian,
Hi Jiange, well that looks correct to me, but seems to be a bit to complicated. What exactly was wrong with version 3?
(1) If you open amdgpu_autodump, use it and close it, then you can't open it again, because wait_for_completion_interruptible_timeout() would decrement amdgpu_autodump.dumping.done to 0, then .open() would always return failure except the first time.
In this case we should probably just use complete_all() instead of just
complete(). So that the struct complete stays in the completed state.
(2) reset lock is not optimal in this case. Because usermode app would take any operation at any time and there are so many race conditions to solve. A dedicated lock would be simpler and clearer.
I don't think that this will work. Using the reset lock is mandatory
here or otherwise we always race between a new process opening the file
and an ongoing GPU reset.
Just imagine what happens when the process which waited for the GPU
reset event doesn't do a dump, but just closes and immediately reopens
the file while the last reset is still ongoing.
What we could do here is using mutex_trylock() on the reset lock and
return -EBUSY when a reset is ongoing. Or maybe better
mutex_lock_interruptible().
Please completely drop this extra check. Waking up the queue and waiting for completion should always work when done right.
This check is very necessary, because if there is no usermode app listening, the following wait_for_completion_interruptible_timeout() would wait until timeout anyway, which is 10 minutes for nothing. This is not what we wanted.
See the wait_event_* documentation, exactly that's what you should never do.
Instead just signal the struct completion with complete_all() directly
after it is created. This way the wakeup is a no-op and waiting for the
struct completion continues immediately.
Regards,
Christian.
Jiange
-----Original Message-----
From: Koenig, Christian <Christian.Koenig@xxxxxxx>
Sent: Wednesday, April 29, 2020 10:09 PM
To: Pelloux-prayer, Pierre-eric <Pierre-eric.Pelloux-prayer@xxxxxxx>; Zhao, Jiange <Jiange.Zhao@xxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx
Cc: Kuehling, Felix <Felix.Kuehling@xxxxxxx>; Deucher, Alexander <Alexander.Deucher@xxxxxxx>; Liu, Monk <Monk.Liu@xxxxxxx>; Zhang, Hawking <Hawking.Zhang@xxxxxxx>
Subject: Re: [PATCH] drm/amdgpu: Add autodump debugfs node for gpu reset v4
Am 29.04.20 um 16:04 schrieb Pierre-Eric Pelloux-Prayer:
Hi Jiange,
This version seems to work fine.
Tested-by: Pierre-Eric Pelloux-Prayer
<pierre-eric.pelloux-prayer@xxxxxxx>
On 29/04/2020 07:08, Zhao, Jiange wrote:
[AMD Official Use Only - Internal Distribution Only]
Hi all,
I worked out the race condition and here is version 5. Please have a look.
Jiange
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*From:* Zhao, Jiange <Jiange.Zhao@xxxxxxx>
*Sent:* Wednesday, April 29, 2020 1:06 PM
*To:* amd-gfx@xxxxxxxxxxxxxxxxxxxxx <amd-gfx@xxxxxxxxxxxxxxxxxxxxx>
*Cc:* Koenig, Christian <Christian.Koenig@xxxxxxx>; Kuehling, Felix
<Felix.Kuehling@xxxxxxx>; Pelloux-prayer, Pierre-eric
<Pierre-eric.Pelloux-prayer@xxxxxxx>; Deucher, Alexander
<Alexander.Deucher@xxxxxxx>; Zhang, Hawking <Hawking.Zhang@xxxxxxx>;
Liu, Monk <Monk.Liu@xxxxxxx>; Zhao, Jiange <Jiange.Zhao@xxxxxxx>
*Subject:* [PATCH] drm/amdgpu: Add autodump debugfs node for gpu
reset v4
From: Jiange Zhao <Jiange.Zhao@xxxxxxx>
When GPU got timeout, it would notify an interested part of an
opportunity to dump info before actual GPU reset.
A usermode app would open 'autodump' node under debugfs system and
poll() for readable/writable. When a GPU reset is due, amdgpu would
notify usermode app through wait_queue_head and give it 10 minutes to
dump info.
After usermode app has done its work, this 'autodump' node is closed.
On node closure, amdgpu gets to know the dump is done through the
completion that is triggered in release().
There is no write or read callback because necessary info can be
obtained through dmesg and umr. Messages back and forth between
usermode app and amdgpu are unnecessary.
v2: (1) changed 'registered' to 'app_listening'
(2) add a mutex in open() to prevent race condition
v3 (chk): grab the reset lock to avoid race in autodump_open,
rename debugfs file to amdgpu_autodump,
provide autodump_read as well,
style and code cleanups
v4: add 'bool app_listening' to differentiate situations, so that
the node can be reopened; also, there is no need to wait for
completion when no app is waiting for a dump.
v5: change 'bool app_listening' to 'enum amdgpu_autodump_state'
add 'app_state_mutex' for race conditions:
(1)Only 1 user can open this file node
(2)wait_dump() can only take effect after poll() executed.
(3)eliminated the race condition between release() and
wait_dump()
Hi Jiange, well that looks correct to me, but seems to be a bit to complicated. What exactly was wrong with version 3?
One more comment below.
Signed-off-by: Jiange Zhao <Jiange.Zhao@xxxxxxx>
---
drivers/gpu/drm/amd/amdgpu/amdgpu.h | 2 +
drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 92
++++++++++++++++++++-
drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.h | 14 ++++
drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 2 +
4 files changed, 109 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index bc1e0fd71a09..6f8ef98c4b97 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -990,6 +990,8 @@ struct amdgpu_device {
char product_number[16];
char product_name[32];
char serial[16];
+
+ struct amdgpu_autodump autodump;
};
static inline struct amdgpu_device *amdgpu_ttm_adev(struct
ttm_bo_device *bdev) diff --git
a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
index 1a4894fa3693..1d4a95e8ad5b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
@@ -27,7 +27,7 @@
#include <linux/pci.h>
#include <linux/uaccess.h>
#include <linux/pm_runtime.h>
-
+#include <linux/poll.h>
#include <drm/drm_debugfs.h>
#include "amdgpu.h"
@@ -74,8 +74,96 @@ int amdgpu_debugfs_add_files(struct amdgpu_device
*adev,
return 0;
}
+int amdgpu_debugfs_wait_dump(struct amdgpu_device *adev) { #if
+defined(CONFIG_DEBUG_FS)
+ unsigned long timeout = 600 * HZ;
+ int ret;
+
+ mutex_lock(&adev->autodump.app_state_mutex);
+ if (adev->autodump.app_state != AMDGPU_AUTODUMP_LISTENING) {
+ mutex_unlock(&adev->autodump.app_state_mutex);
+ return 0;
+ }
+ mutex_unlock(&adev->autodump.app_state_mutex);
Please completely drop this extra check. Waking up the queue and waiting for completion should always work when done right.
Regards,
Christian.
+
+ wake_up_interruptible(&adev->autodump.gpu_hang);
+
+ ret =
+wait_for_completion_interruptible_timeout(&adev->autodump.dumping,
+timeout);
+ if (ret == 0) {
+ pr_err("autodump: timeout, move on to gpu
+recovery\n");
+ return -ETIMEDOUT;
+ }
+#endif
+ return 0;
+}
+
#if defined(CONFIG_DEBUG_FS)
+static int amdgpu_debugfs_autodump_open(struct inode *inode, struct
+file *file) {
+ struct amdgpu_device *adev = inode->i_private;
+ int ret;
+
+ file->private_data = adev;
+
+ mutex_lock(&adev->autodump.app_state_mutex);
+ if (adev->autodump.app_state == AMDGPU_AUTODUMP_NO_APP) {
+ adev->autodump.app_state =
+AMDGPU_AUTODUMP_REGISTERED;
+ ret = 0;
+ } else {
+ ret = -EBUSY;
+ }
+ mutex_unlock(&adev->autodump.app_state_mutex);
+
+ return ret;
+}
+
+static int amdgpu_debugfs_autodump_release(struct inode *inode,
+struct file *file) {
+ struct amdgpu_device *adev = file->private_data;
+
+ mutex_lock(&adev->autodump.app_state_mutex);
+ complete(&adev->autodump.dumping);
+ adev->autodump.app_state = AMDGPU_AUTODUMP_NO_APP;
+ mutex_unlock(&adev->autodump.app_state_mutex);
+ return 0;
+}
+
+static unsigned int amdgpu_debugfs_autodump_poll(struct file *file,
+struct poll_table_struct *poll_table) {
+ struct amdgpu_device *adev = file->private_data;
+
+ mutex_lock(&adev->autodump.app_state_mutex);
+ poll_wait(file, &adev->autodump.gpu_hang, poll_table);
+ adev->autodump.app_state = AMDGPU_AUTODUMP_LISTENING;
+ mutex_unlock(&adev->autodump.app_state_mutex);
+
+ if (adev->in_gpu_reset)
+ return POLLIN | POLLRDNORM | POLLWRNORM;
+
+ return 0;
+}
+
+static const struct file_operations autodump_debug_fops = {
+ .owner = THIS_MODULE,
+ .open = amdgpu_debugfs_autodump_open,
+ .poll = amdgpu_debugfs_autodump_poll,
+ .release = amdgpu_debugfs_autodump_release, };
+
+static void amdgpu_debugfs_autodump_init(struct amdgpu_device *adev)
+{
+ init_completion(&adev->autodump.dumping);
+ init_waitqueue_head(&adev->autodump.gpu_hang);
+ adev->autodump.app_state = AMDGPU_AUTODUMP_NO_APP;
+ mutex_init(&adev->autodump.app_state_mutex);
+
+ debugfs_create_file("amdgpu_autodump", 0600,
+ adev->ddev->primary->debugfs_root,
+ adev, &autodump_debug_fops); }
+
/**
* amdgpu_debugfs_process_reg_op - Handle MMIO register
reads/writes
*
@@ -1434,6 +1522,8 @@ int amdgpu_debugfs_init(struct amdgpu_device
*adev)
amdgpu_ras_debugfs_create_all(adev);
+ amdgpu_debugfs_autodump_init(adev);
+
return amdgpu_debugfs_add_files(adev, amdgpu_debugfs_list,
ARRAY_SIZE(amdgpu_debugfs_list));
}
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.h
b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.h
index de12d1101526..51b4ea790686 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.h
@@ -31,6 +31,19 @@ struct amdgpu_debugfs {
unsigned num_files;
};
+enum amdgpu_autodump_state {
+ AMDGPU_AUTODUMP_NO_APP,
+ AMDGPU_AUTODUMP_REGISTERED,
+ AMDGPU_AUTODUMP_LISTENING
+};
+
+struct amdgpu_autodump {
+ struct mutex app_state_mutex;
+ enum amdgpu_autodump_state app_state;
+ struct completion dumping;
+ struct wait_queue_head gpu_hang; };
+
int amdgpu_debugfs_regs_init(struct amdgpu_device *adev);
int amdgpu_debugfs_init(struct amdgpu_device *adev);
void amdgpu_debugfs_fini(struct amdgpu_device *adev); @@ -40,3
+53,4 @@ int amdgpu_debugfs_add_files(struct amdgpu_device *adev,
int amdgpu_debugfs_fence_init(struct amdgpu_device *adev);
int amdgpu_debugfs_firmware_init(struct amdgpu_device *adev);
int amdgpu_debugfs_gem_init(struct amdgpu_device *adev);
+int amdgpu_debugfs_wait_dump(struct amdgpu_device *adev);
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index e6978a2c26b7..8109946075b1 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -3912,6 +3912,8 @@ static int amdgpu_device_pre_asic_reset(struct
amdgpu_device *adev,
int i, r = 0;
bool need_full_reset = *need_full_reset_arg;
+ amdgpu_debugfs_wait_dump(adev);
+
/* block all schedulers and reset given job's ring */
for (i = 0; i < AMDGPU_MAX_RINGS; ++i) {
struct amdgpu_ring *ring = adev->rings[i];
--
2.20.1
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