[DISPATCH-2203] Alloc_pool_item_t sequence number should be atomic

• Type: Test
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 1.16.1, 1.18.0
• Component/s: Router Node
• Labels: race-condition
• Assignee: Unassigned
• Reporter: Charles E. Rolke
• Created: 19/Jul/21 14:23
• Updated: 29/Jan/22 16:00

Description

Alloc pool uses a sequence number for safe pointer dereferencing.

Definition
  Line 55: uintmax_t sequence;  // uintmax_t ensures proper alignment of following data
In qd_alloc:
  Line 406: item->sequence = 0;
in qd_dealloc:
  Line 477: item->sequence++;
In qd_alloc_sequence:
  Line 525: reuturn item->sequence;

It is reasonably certain that multiple threads will be referencing the same item at nearly the same time. The code as shown gets flagged by tsan.

Issue Links

• duplicates: DISPATCH-2320 TSAN: alloc sequence is non-atomic