[Lldb-commits] [lldb] Use a fallback interval strategy for the task_for_pid request. (PR #217425)

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llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-lldb

Author: jimingham

<details>
<summary>Changes</summary>

We've seen cases on heavily loaded bots where task_for_pid requests get denied because the authentication system is overloaded.  Use an increasing timeout to avoid piling on when this is happening.

The fallback I chose does:

0: 0.01
1: 0.02
2: 0.04
3: 0.07
4: 0.11
5: 0.16
6: 0.22
7: 0.29
8: 0.37
9: 0.46

which seems reasonable to me.  At worst this will wait about a second, which is still below our test launch timeouts.


---
Full diff: https://github.com/llvm/llvm-project/pull/217425.diff


1 Files Affected:

- (modified) lldb/tools/debugserver/source/MacOSX/MachTask.mm (+8-1) 


``````````diff
diff --git a/lldb/tools/debugserver/source/MacOSX/MachTask.mm b/lldb/tools/debugserver/source/MacOSX/MachTask.mm
index 22ad0c407de42..c7b589abaa5e4 100644
--- a/lldb/tools/debugserver/source/MacOSX/MachTask.mm
+++ b/lldb/tools/debugserver/source/MacOSX/MachTask.mm
@@ -529,6 +529,8 @@ static void get_threads_profile_data(DNBProfileDataScanType scanType,
     DNBError err;
     mach_port_t task_self = mach_task_self();
     task_t task = TASK_NULL;
+    uint32_t interval = k_usec_delay;
+
     for (uint32_t i = 0; i < k_num_retries; i++) {
       DNBLog("[LaunchAttach] (%d) about to task_for_pid(%d)", getpid(), pid);
       err = ::task_for_pid(task_self, pid, &task);
@@ -556,7 +558,12 @@ static void get_threads_profile_data(DNBProfileDataScanType scanType,
       }
 
       // Sleep a bit and try again
-      ::usleep(k_usec_delay);
+      // Use an increasing interval so that if there's a short term traffic
+      // jam, we skip past rather than exacerbating it.  We see this sequence
+      // timing out occasionally on heavily loaded bots, seemingly because the
+      // syspolicyd isn't keeping up.
+      interval += k_usec_delay * i;
+      ::usleep(interval);
     }
   }
   return TASK_NULL;

``````````

</details>


https://github.com/llvm/llvm-project/pull/217425