On 2020-10-22 19:04, Peter Zijlstra wrote:
On Thu, Oct 22, 2020 at 06:19:37PM +0530, Sai Prakash Ranjan wrote:
On 2020-10-22 17:02, Peter Zijlstra wrote:
On Thu, Oct 22, 2020 at 04:27:52PM +0530, Sai Prakash Ranjan wrote:
Looking at the ETR and other places in the kernel, ETF and the ETB are the only places trying to dereference the task(owner) in tmc_enable_etf_sink_perf() which is also called from the sched_in path as in the call trace.
@@ -391,6 +392,10 @@ static void *tmc_alloc_etf_buffer(struct coresight_device *csdev, { int node; struct cs_buffers *buf;
- struct task_struct *task = READ_ONCE(event->owner);
- if (!task || is_kernel_event(event))
return NULL;This is *wrong*... why do you care about who owns the events?
The original issue was the owner being NULL and causing a NULL pointer dereference. I did ask some time back if it is valid for the owner to be NULL [1] and should probably be handled in events core?
No, what I asked is why do you care about ->owner to begin with? That seems wrong. A driver should not touch ->owner _at_all_.
Ah ok, so Suzuki explained that in other reply and if there is some other better way?
Thanks, Sai