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Update tsan suppressions and fix a race in gc_start #13964

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Merged
merged 3 commits into from
Jul 22, 2025
+20 −25
Merged

Update tsan suppressions and fix a race in gc_start #13964

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06e19e3
Fix TSAN data race in gc_start
jhawthorn Jul 18, 2025
828d633
Update misc/tsan_suppressions.txt
jhawthorn Jul 18, 2025
6bef20c
Merge branch 'master' into tsan_cleanup
jhawthorn Jul 22, 2025
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6 changes: 3 additions & 3 deletions gc/default/default.c
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Original file line number Diff line number Diff line change
Expand Up @@ -6316,9 +6316,6 @@ gc_start(rb_objspace_t *objspace, unsigned int reason)
{
unsigned int do_full_mark = !!(reason & GPR_FLAG_FULL_MARK);

/* reason may be clobbered, later, so keep set immediate_sweep here */
objspace->flags.immediate_sweep = !!(reason & GPR_FLAG_IMMEDIATE_SWEEP);

if (!rb_darray_size(objspace->heap_pages.sorted)) return TRUE; /* heap is not ready */
if (!(reason & GPR_FLAG_METHOD) && !ready_to_gc(objspace)) return TRUE; /* GC is not allowed */

Expand All @@ -6329,6 +6326,9 @@ gc_start(rb_objspace_t *objspace, unsigned int reason)
unsigned int lock_lev;
gc_enter(objspace, gc_enter_event_start, &lock_lev);

/* reason may be clobbered, later, so keep set immediate_sweep here */
objspace->flags.immediate_sweep = !!(reason & GPR_FLAG_IMMEDIATE_SWEEP);

#if RGENGC_CHECK_MODE >= 2
gc_verify_internal_consistency(objspace);
#endif
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39 changes: 17 additions & 22 deletions misc/tsan_suppressions.txt
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Expand Up @@ -37,22 +37,16 @@ race_top:rb_ec_vm_lock_rec
race_top:vm_lock_enter
race_top:vm_locked

# Ractors
race:ractor_take
race:ractor_register_take
race:ractor_check_take_basket
race:ractor_selector__wait

# vm->ractor.sched.grq_cnt++
race_top:ractor_sched_enq
race_top:ractor_sched_deq

# Using VM lock instead of rb_native_mutex_unlock?
# Race between vm_remove_ractor writing ractor count and
# native_thread_check_and_create_shared reading it during thread creation.
# The write happens when a ractor thread exits, the read happens when
# checking if new shared threads need to be created.
race:vm_remove_ractor

# cr->sync.wait.wakeup_status
race_top:rb_ractor_sched_sleep

# th->sched.finished at end of co_start
race_top:rb_thread_sched_mark_zombies

Expand All @@ -62,9 +56,6 @@ race_top:thread_sched_wait_events
# At thread start
race_top:rb_ractor_set_current_ec_

# Possible deadlock between Ractor lock and UBF lock
deadlock:ractor_sleep_interrupt

# TSan reports a lock-order-inversion between thread_sched_lock_ and this lock.
# It's unclear if that can cause a deadlock since the lock is on self
deadlock:ractor_lock_self
Expand All @@ -76,16 +67,22 @@ deadlock:rb_ractor_sched_barrier_start
# RVALUE_AGE_SET manipulates flag bits on objects which may be accessed in Ractors
race_top:RVALUE_AGE_SET

# Inline caches
# Inline caches and call cache updates
# Multiple threads can race when updating shared call caches during method lookups
# and argument forwarding. These races involve reading/writing cd->cc fields.
race_top:vm_cc_call_set
race_top:vm_cc_class_check
race_top:vm_search_cc
race_top:vm_search_method_slowpath0
race_top:rb_vm_opt_getconstant_path
race_top:vm_ic_attr_index_set
race:vm_ic_update
race:vm_caller_setup_fwd_args

# Shapes have problems with RCLASS_MAX_IV_COUNT and RCLASS_VARIATION_COUNT
# which are probably benign
# Race in shape_get_next where multiple threads simultaneously access and modify
# RCLASS_MAX_IV_COUNT and RCLASS_VARIATION_COUNT fields in class objects.
# One thread reads the field while another thread calls RCLASS_SET_MAX_IV_COUNT.
# This happens during instance variable shape transitions in multi-threaded code.
race:shape_get_next

# Non-atomic reads/writes
Expand All @@ -99,16 +96,10 @@ race:rb_ec_cleanup
# timer thread
race:after_fork_ruby

# object_id races
race:object_id

# Sets objspace->flags.dont_incremental while writebarrier may be running
race_top:objspace_each_exec
race_top:objspace_each_objects_ensure

# Ractor autoload
race:rb_ractor_autoload_load

# Non-atomic lazy initialized static variable
race_top:rbimpl_intern_const

Expand All @@ -123,3 +114,7 @@ race:rb_tracepoint_enable
# We walk the machine stack looking for markable objects, a thread with the GVL
# released could by mutating the stack with non-Ruby-objects
race:rb_gc_mark_machine_context

# GC enable/disable flag modifications race with object allocation flag reads
race_top:rb_gc_impl_gc_disable
race_top:rb_gc_impl_gc_enable
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