threads deadlock caught locally: missing safe region in _jl_mutex_wait

[vtjnash]

(rr trace available upon request)

Looks like _jl_mutex_wait fails to enter a gc-safe region inside when jl_running_under_rr is true, causing deadlocks in this situation:

# this thread (tid 50) wants GC to start (waiting on tid 1 to enter gc-safe)
unknown function (ip: 0x7fbe26a5d115) at /lib/x86_64-linux-gnu/libc.so.6                                                                                                                               
pthread_cond_wait at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)                                                                                                                                    
uv_cond_wait at /workspace/srcdir/libuv/src/unix/thread.c:822                                                                                                                                          
jl_gc_wait_for_the_world at /home/vtjnash/julia1/src/safepoint.c:154                                                                                                                                   
ijl_gc_collect at /home/vtjnash/julia1/src/gc-stock.c:3362                                                                                                                                             
gc at ./gcutils.jl:133 [inlined]                                                                                                                                                                       
cl at /home/vtjnash/julia1/test/threads.jl:466                                                                                                                                                         
#70 at /home/vtjnash/julia1/test/threads.jl:488                                                                                                                                                        
unknown function (ip: 0x7fbe0cb75dd5) at (unknown file)                                                                                                                                                
unknown function (ip: 0x7fbe26a60ac2) at /lib/x86_64-linux-gnu/libc.so.6                                                                                                                               
clone at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)                                                                                                                                                
unknown function (ip: (nil)) at (unknown file)                                                                                                                                                         
unknown function (ip: 0x7fbe26a5d115) at /lib/x86_64-linux-gnu/libc.so.6                                                                                                                               
pthread_cond_wait at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)                                                                                                                                    
uv_cond_wait at /workspace/srcdir/libuv/src/unix/thread.c:822                                                                                                                                          
ijl_task_get_next at /home/vtjnash/julia1/src/scheduler.c:520                                      
poptask at ./task.jl:1163                                                                          
wait at ./task.jl:1172                                                                             
#wait#550 at ./condition.jl:141                                                                    
wait at ./condition.jl:136 [inlined]                                                               
take_buffered at ./channels.jl:533                                                                 
take! at ./channels.jl:527 [inlined]                                                               
#56 at /home/vtjnash/julia1/test/threads.jl:446                                                    
init_perthread at ./lock.jl:789                                                                    
getindex at ./lock.jl:746 [inlined]                                                                
OncePerThread at ./lock.jl:739 [inlined]                                                           
cl at /home/vtjnash/julia1/test/threads.jl:469                                                     
#70 at /home/vtjnash/julia1/test/threads.jl:488                                                    
unknown function (ip: 0x7fbe0cb75dd5) at (unknown file)                                            
unknown function (ip: 0x7fbe26a60ac2) at /lib/x86_64-linux-gnu/libc.so.6                           
clone at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)                                            
unknown function (ip: (nil)) at (unknown file)                                                     

# this thread (tid 1) wants the iolock to finish running finalizers (waiting on tid 0 to release)
unknown function (ip: 0x7fbe26a5d115) at /lib/x86_64-linux-gnu/libc.so.6                                                                                                                               
pthread_cond_wait at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)                                                                                                                                    
uv_cond_wait at /workspace/srcdir/libuv/src/unix/thread.c:822                                                                                                                                          
_jl_mutex_wait at /home/vtjnash/julia1/src/threading.c:925                                                                                                                                             
_jl_mutex_lock at /home/vtjnash/julia1/src/threading.c:957                                                                                                                                             
jl_mutex_lock at /home/vtjnash/julia1/src/julia_locks.h:65 [inlined]                                                                                                                                   
JL_UV_LOCK at /home/vtjnash/julia1/src/jl_uv.c:137 [inlined]                                                                                                                                           
ijl_iolock_begin at /home/vtjnash/julia1/src/jl_uv.c:147                                                                                                                                               
iolock_begin at ./libuv.jl:48 [inlined]                                                                                                                                                                
uvfinalize at ./asyncevent.jl:200                                                                                                                                                                      
jfptr_uvfinalize_97523 at /home/vtjnash/julia1/usr/lib/julia/sys.so (unknown line)                                                                                                                     
_jl_invoke at /home/vtjnash/julia1/src/gf.c:3306 [inlined]                                                                                                                                             
ijl_apply_generic at /home/vtjnash/julia1/src/gf.c:3494                                                                                                                                                
run_finalizer at /home/vtjnash/julia1/src/gc-common.c:180                                                                                                                                              
jl_gc_run_finalizers_in_list at /home/vtjnash/julia1/src/gc-common.c:270                                                                                                                               
run_finalizers at /home/vtjnash/julia1/src/gc-common.c:316                                                                                                                                             
ijl_gc_collect at /home/vtjnash/julia1/src/gc-stock.c:3400                                                                                                                                             
gc at ./gcutils.jl:133 [inlined]                                                                                                                                                                       
cl at /home/vtjnash/julia1/test/threads.jl:466                                                                                                                                                         
#70 at /home/vtjnash/julia1/test/threads.jl:488                                                                                                                                                        
unknown function (ip: 0x7fbe0cb75dd5) at (unknown file)                                                                                                                                                
unknown function (ip: 0x7fbe26a60ac2) at /lib/x86_64-linux-gnu/libc.so.6                                                                                                                               
clone at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)                                                                                                                                                
unknown function (ip: (nil)) at (unknown file)

# this thread (tid 0) is holding the iolock waiting to hear that gc is finished (waiting on tid 50)
unknown function (ip: 0x7fbe26a5d115) at /lib/x86_64-linux-gnu/libc.so.6                                                                                                                               
pthread_cond_wait at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)                                                                                                                                    
uv_cond_wait at /workspace/srcdir/libuv/src/unix/thread.c:822                                                                                                                                          
jl_safepoint_wait_gc at /home/vtjnash/julia1/src/safepoint.c:246                                                                                                                                       
jl_set_gc_and_wait at /home/vtjnash/julia1/src/safepoint.c:226                                                                                                                                         
segv_handler at /home/vtjnash/julia1/src/signals-unix.c:395 [inlined]                                                                                                                                  
segv_handler at /home/vtjnash/julia1/src/signals-unix.c:381                                                                                                                                            
unknown function (ip: 0x7fbe26a0e51f) at /lib/x86_64-linux-gnu/libc.so.6                           
ijl_gc_safepoint at /home/vtjnash/julia1/src/jlapi.c:740                                           
ijl_task_get_next at /home/vtjnash/julia1/src/scheduler.c:456                                      
poptask at ./task.jl:1163                                                                          
wait at ./task.jl:1172                                                                             
#wait#550 at ./condition.jl:141                                                                    
wait at ./condition.jl:136 [inlined]                                                               
take_buffered at ./channels.jl:533                                                                 
take! at ./channels.jl:527                                                                         
unknown function (ip: 0x7fbe0cb707f2) at (unknown file)                                            
_jl_invoke at /home/vtjnash/julia1/src/gf.c:3306 [inlined]                                         
ijl_apply_generic at /home/vtjnash/julia1/src/gf.c:3494                                            
jl_apply at /home/vtjnash/julia1/src/julia.h:2240 [inlined]                                        
do_call at /home/vtjnash/julia1/src/interpreter.c:125                                              
eval_value at /home/vtjnash/julia1/src/interpreter.c:223                                           
eval_body at /home/vtjnash/julia1/src/interpreter.c:567                                            
eval_body at /home/vtjnash/julia1/src/interpreter.c:544                                            
jl_interpret_toplevel_thunk at /home/vtjnash/julia1/src/interpreter.c:894                          
jl_toplevel_eval_flex at /home/vtjnash/julia1/src/toplevel.c:1065                                  
jl_toplevel_eval_flex at /home/vtjnash/julia1/src/toplevel.c:1005                                  
ijl_toplevel_eval at /home/vtjnash/julia1/src/toplevel.c:1076                                      
ijl_toplevel_eval_in at /home/vtjnash/julia1/src/toplevel.c:1118                                   
eval at ./boot.jl:460                            
include_string at ./loading.jl:2839              
_jl_invoke at /home/vtjnash/julia1/src/gf.c:3306 [inlined]                                         
ijl_apply_generic at /home/vtjnash/julia1/src/gf.c:3494                                            
_include at ./loading.jl:2899                    
include at ./Base.jl:300                         
macro expansion at /home/vtjnash/julia1/test/testdefs.jl:33 [inlined]                              
macro expansion at /home/vtjnash/julia1/usr/share/julia/stdlib/v1.12/Test/src/Test.jl:1700 [inlined]                                                                                                   
macro expansion at /home/vtjnash/julia1/test/testdefs.jl:26 [inlined]