Hi!
As the error capture will compress user buffers as directed to by the user, it can take an arbitrary amount of time and space. Break up the compression loops with a call to cond_resched(), that will allow other processes to schedule (avoiding the soft lockups) and also serve as a warning should we try to make this loop atomic in the future.
Signed-off-by: Chris Wilson chris@chris-wilson.co.uk Cc: Mika Kuoppala mika.kuoppala@linux.intel.com Cc: stable@vger.kernel.org Reviewed-by: Mika Kuoppala mika.kuoppala@linux.intel.com
This was queued for 4.19-stable, but is very likely wrong.
@@ -397,6 +399,7 @@ static int compress_page(struct i915_vma_compress *c, if (!(wc && i915_memcpy_from_wc(ptr, src, PAGE_SIZE))) memcpy(ptr, src, PAGE_SIZE); dst->pages[dst->page_count++] = ptr;
- cond_resched();
return 0; }
4.19 compress_page begins with
static int compress_page(struct compress *c, ... page = __get_free_page(GFP_ATOMIC | __GFP_NOWARN);
and likely may not sleep. That changed with commit a42f45a2a85998453078, but that one is not present in 4.19..
I believe we don't need this in stable: dumping of error file will not take so long to trigger softlockup detectors... and if userland access blocked, we would be able to reschedule, anyway.
Best regards, Pavel