[WIP] Fix @Shopify/ruby/issues/703 -- remove the temporary workaround in zjit/src/hir.rs and fix the crash #3
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Don't abort the entire compilation. Fix Shopify#700
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tekknolagi due to an error
August 25, 2025 15:11
tekknolagi
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If we malloc when the current Ractor is locked, we can deadlock because
GC requires VM lock and Ractor barrier. If another Ractor is waiting on
this Ractor lock, then it will deadlock because the other Ractor will
never join the barrier.
For example, this script deadlocks:
r = Ractor.new do
loop do
Ractor::Port.new
end
end
100000.times do |i|
r.send(nil)
puts i
end
On debug builds, it fails with this assertion error:
vm_sync.c:75: Assertion Failed: vm_lock_enter:cr->sync.locked_by != rb_ractor_self(cr)
On non-debug builds, we can see that it deadlocks in the debugger:
Main Ractor:
frame #3: 0x000000010021fdc4 miniruby`rb_native_mutex_lock(lock=<unavailable>) at thread_pthread.c:115:14
frame Shopify#4: 0x0000000100193eb8 miniruby`ractor_send0 [inlined] ractor_lock(r=<unavailable>, file=<unavailable>, line=1180) at ractor.c:73:5
frame Shopify#5: 0x0000000100193eb0 miniruby`ractor_send0 [inlined] ractor_send_basket(ec=<unavailable>, rp=0x0000000131092840, b=0x000000011c63de80, raise_on_error=true) at ractor_sync.c:1180:5
frame Shopify#6: 0x0000000100193eac miniruby`ractor_send0(ec=<unavailable>, rp=0x0000000131092840, obj=4, move=<unavailable>, raise_on_error=true) at ractor_sync.c:1211:5
Second Ractor:
frame #2: 0x00000001002208d0 miniruby`rb_ractor_sched_barrier_start [inlined] rb_native_cond_wait(cond=<unavailable>, mutex=<unavailable>) at thread_pthread.c:221:13
frame #3: 0x00000001002208cc miniruby`rb_ractor_sched_barrier_start(vm=0x000000013180d600, cr=0x0000000131093460) at thread_pthread.c:1438:13
frame Shopify#4: 0x000000010028a328 miniruby`rb_vm_barrier at vm_sync.c:262:13 [artificial]
frame Shopify#5: 0x00000001000dfa6c miniruby`gc_start [inlined] rb_gc_vm_barrier at gc.c:179:5
frame Shopify#6: 0x00000001000dfa68 miniruby`gc_start [inlined] gc_enter(objspace=0x000000013180fc00, event=gc_enter_event_start, lock_lev=<unavailable>) at default.c:6636:9
frame Shopify#7: 0x00000001000dfa48 miniruby`gc_start(objspace=0x000000013180fc00, reason=<unavailable>) at default.c:6361:5
frame Shopify#8: 0x00000001000e3fd8 miniruby`objspace_malloc_increase_body [inlined] garbage_collect(objspace=0x000000013180fc00, reason=512) at default.c:6341:15
frame Shopify#9: 0x00000001000e3fa4 miniruby`objspace_malloc_increase_body [inlined] garbage_collect_with_gvl(objspace=0x000000013180fc00, reason=512) at default.c:6741:16
frame Shopify#10: 0x00000001000e3f88 miniruby`objspace_malloc_increase_body(objspace=0x000000013180fc00, mem=<unavailable>, new_size=<unavailable>, old_size=<unavailable>, type=<unavailable>) at default.c:8007:13
frame Shopify#11: 0x00000001000e3c44 miniruby`rb_gc_impl_malloc [inlined] objspace_malloc_fixup(objspace=0x000000013180fc00, mem=0x000000011c700000, size=12582912) at default.c:8085:5
frame Shopify#12: 0x00000001000e3c30 miniruby`rb_gc_impl_malloc(objspace_ptr=0x000000013180fc00, size=12582912) at default.c:8182:12
frame Shopify#13: 0x00000001000d4584 miniruby`ruby_xmalloc [inlined] ruby_xmalloc_body(size=<unavailable>) at gc.c:5128:12
frame Shopify#14: 0x00000001000d4568 miniruby`ruby_xmalloc(size=<unavailable>) at gc.c:5118:34
frame Shopify#15: 0x00000001001eb184 miniruby`rb_st_init_existing_table_with_size(tab=0x000000011c2b4b40, type=<unavailable>, size=<unavailable>) at st.c:559:39
frame Shopify#16: 0x00000001001ebc74 miniruby`rebuild_table_if_necessary [inlined] rb_st_init_table_with_size(type=0x00000001004f4a78, size=524287) at st.c:585:5
frame Shopify#17: 0x00000001001ebc5c miniruby`rebuild_table_if_necessary [inlined] rebuild_table(tab=0x000000013108e2f0) at st.c:753:19
frame Shopify#18: 0x00000001001ebbfc miniruby`rebuild_table_if_necessary(tab=0x000000013108e2f0) at st.c:1125:9
frame Shopify#19: 0x00000001001eba08 miniruby`rb_st_insert(tab=0x000000013108e2f0, key=262144, value=4767566624) at st.c:1143:5
frame Shopify#20: 0x0000000100194b84 miniruby`ractor_port_initialzie [inlined] ractor_add_port(r=0x0000000131093460, id=262144) at ractor_sync.c:399:9
frame Shopify#21: 0x0000000100194b58 miniruby`ractor_port_initialzie [inlined] ractor_port_init(rpv=4750065560, r=0x0000000131093460) at ractor_sync.c:87:5
frame Shopify#22: 0x0000000100194b34 miniruby`ractor_port_initialzie(self=4750065560) at ractor_sync.c:103:12
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tekknolagi
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We need to free the current_block_exits in parse_program when we're done
with it to prevent memory leaks. This fixes the following memory leak detected
when running Ruby using `RUBY_FREE_AT_EXIT=1 ruby -nc -e "break"`:
Direct leak of 32 byte(s) in 1 object(s) allocated from:
#0 0x5bd3c5bc66c8 in realloc (miniruby+0x616c8) (BuildId: ruby/prism@ba6a96e5a060)
#1 0x5bd3c5f91fd9 in pm_node_list_grow prism/templates/src/node.c.erb:35:40
#2 0x5bd3c5f91e9d in pm_node_list_append prism/templates/src/node.c.erb:48:9
#3 0x5bd3c6001fa0 in parse_block_exit prism/prism.c:15788:17
Shopify#4 0x5bd3c5fee155 in parse_expression_prefix prism/prism.c:19221:50
Shopify#5 0x5bd3c5fe9970 in parse_expression prism/prism.c:22235:23
Shopify#6 0x5bd3c5fe0586 in parse_statements prism/prism.c:13976:27
Shopify#7 0x5bd3c5fd6792 in parse_program prism/prism.c:22508:40
ruby/prism@fdf9b8d24a
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Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.
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