[PATCH v4 1/3] venus: core: handle race condititon for core ops

From: Mansur Alisha Shaik
Date: Wed Sep 16 2020 - 04:50:18 EST

For core ops we are having only write protect but there
is no read protect, because of this in multthreading
and concurrency, one CPU core is reading without wait
which is causing the NULL pointer dereferece crash.

one such scenario is as show below, where in one CPU
core, core->ops becoming NULL and in another CPU core
calling core->ops->session_init().

CPU: core-7:
Call trace:
hfi_session_init+0x180/0x1dc [venus_core]
vdec_queue_setup+0x9c/0x364 [venus_dec]
vb2_core_reqbufs+0x1e4/0x368 [videobuf2_common]
vb2_reqbufs+0x4c/0x64 [videobuf2_v4l2]
v4l2_m2m_reqbufs+0x50/0x84 [v4l2_mem2mem]
v4l2_m2m_ioctl_reqbufs+0x2c/0x38 [v4l2_mem2mem]

CPU: core-0:
Call trace:
venus_shutdown+0x98/0xfc [venus_core]
venus_sys_error_handler+0x64/0x148 [venus_core]

Signed-off-by: Mansur Alisha Shaik <mansur@xxxxxxxxxxxxxx>
Acked-by: Stanimir Varbanov <stanimir.varbanov@xxxxxxxxxx>
Changes in V4:
- Addressed review comments by Stan in patch series
and combining this change along with shutdown callback
as we are facing race conditions with shutdown callback

drivers/media/platform/qcom/venus/hfi.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/media/platform/qcom/venus/hfi.c b/drivers/media/platform/qcom/venus/hfi.c
index a59022a..58d4c06 100644
--- a/drivers/media/platform/qcom/venus/hfi.c
+++ b/drivers/media/platform/qcom/venus/hfi.c
@@ -195,19 +195,34 @@ EXPORT_SYMBOL_GPL(hfi_session_create);
int hfi_session_init(struct venus_inst *inst, u32 pixfmt)
struct venus_core *core = inst->core;
- const struct hfi_ops *ops = core->ops;
+ const struct hfi_ops *ops;
int ret;

+ /*
+ * If core shutdown is in progress or if we are in system
+ * recovery, return an error as during system error recovery
+ * session_init() can't pass successfully
+ */
+ mutex_lock(&core->lock);
+ if (!core->ops || core->sys_error) {
+ mutex_unlock(&core->lock);
+ return -EIO;
+ }
+ mutex_unlock(&core->lock);
if (inst->state != INST_UNINIT)
return -EINVAL;

inst->hfi_codec = to_codec_type(pixfmt);

+ mutex_lock(&core->lock);
+ ops = core->ops;
ret = ops->session_init(inst, inst->session_type, inst->hfi_codec);
if (ret)
return ret;

+ mutex_unlock(&core->lock);
ret = wait_session_msg(inst);
if (ret)
return ret;
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