task-comm-15 fails when run with multiple threads

[brson]

With RUST_THREADS=16, task-comm-15 occasionally produces valgrind errors like

==8944== Thread 3:
==8944== Invalid read of size 4
==8944==    at 0x4AC73CD: pthread_mutex_lock (pthread_mutex_lock.c:50)
==8944==    by 0x4A2E415: pthread_mutex_lock (forward.c:182)
==8944==    by 0x48E0D27: lock_and_signal::lock() (lock_and_signal.cpp:46)
==8944==    by 0x48E10C1: scoped_lock::scoped_lock(lock_and_signal&) (lock_and_signal.cpp:121)
==8944==    by 0x48E7BF8: rust_chan::send(void*) (rust_chan.cpp:82)
==8944==    by 0x48E9D11: upcall_send (rust_upcall.cpp:203)
==8944==    by 0x8048A24: start (in /home/banderson/Dev/rust/build/test/run-pass/task-comm-15.stage1)
==8944==    by 0x8048DD7: main::spawn_wrapper5 (in /home/banderson/Dev/rust/build/test/run-pass/task-comm-15.stage1)
==8944==    by 0x48E72B0: task_start_wrapper (rust_task.cpp:128)
==8944==    by 0xDEADBEEE: ???
==8944==  Address 0x712bebc is 132 bytes inside a block of size 152 free'd
==8944==    at 0x48CCC02: free (vg_replace_malloc.c:366)
==8944==    by 0x48EE42C: rust_srv::free(void*) (rust_srv.cpp:12)
==8944==    by 0x48F14E1: memory_region::free(void*) (memory_region.cpp:58)
==8944==    by 0x48EE9D6: rust_kernel::free(void*) (rust_kernel.cpp:213)
==8944==    by 0x48E95E9: upcall_del_port (rust_internal.h:173)
==8944==    by 0x8048F88: glue_free11 (in /home/banderson/Dev/rust/build/test/run-pass/task-comm-15.stage1)
==8944==    by 0x8048F42: glue_drop10 (in /home/banderson/Dev/rust/build/test/run-pass/task-comm-15.stage1)
==8944==    by 0x8048C63: _rust_main (in /home/banderson/Dev/rust/build/test/run-pass/task-comm-15.stage1)
==8944==    by 0x8048FBB: _rust_main_wrap (in /home/banderson/Dev/rust/build/test/run-pass/task-comm-15.stage1)
==8944==    by 0xDEADBEEE: ???
==8944==
==8944== Invalid read of size 4
==8944==    at 0x4AC6DAF: __pthread_mutex_lock_full (pthread_mutex_lock.c:139)
==8944==    by 0x4A2E415: pthread_mutex_lock (forward.c:182)
==8944==    by 0x48E0D27: lock_and_signal::lock() (lock_and_signal.cpp:46)
==8944==    by 0x48E10C1: scoped_lock::scoped_lock(lock_and_signal&) (lock_and_signal.cpp:121)
==8944==    by 0x48E7BF8: rust_chan::send(void*) (rust_chan.cpp:82)
==8944==    by 0x48E9D11: upcall_send (rust_upcall.cpp:203)
==8944==    by 0x8048A24: start (in /home/banderson/Dev/rust/build/test/run-pass/task-comm-15.stage1)
==8944==    by 0x8048DD7: main::spawn_wrapper5 (in /home/banderson/Dev/rust/build/test/run-pass/task-comm-15.stage1)
==8944==    by 0x48E72B0: task_start_wrapper (rust_task.cpp:128)
==8944==    by 0xDEADBEEE: ???
==8944==  Address 0x712bebc is 132 bytes inside a block of size 152 free'd
==8944==    at 0x48CCC02: free (vg_replace_malloc.c:366)
==8944==    by 0x48EE42C: rust_srv::free(void*) (rust_srv.cpp:12)
==8944==    by 0x48F14E1: memory_region::free(void*) (memory_region.cpp:58)
==8944==    by 0x48EE9D6: rust_kernel::free(void*) (rust_kernel.cpp:213)
==8944==    by 0x48E95E9: upcall_del_port (rust_internal.h:173)
==8944==    by 0x8048F88: glue_free11 (in /home/banderson/Dev/rust/build/test/run-pass/task-comm-15.stage1)
==8944==    by 0x8048F42: glue_drop10 (in /home/banderson/Dev/rust/build/test/run-pass/task-comm-15.stage1)
==8944==    by 0x8048C63: _rust_main (in /home/banderson/Dev/rust/build/test/run-pass/task-comm-15.stage1)

[msullivan]

Is this still true with the new reworking of tasking and channels?

[msullivan]

It looks like this is caused by #627.

[msullivan]

I ran this test a lot and didn't get any failures. Between that and having identified #627 as the original root cause, I'm going to close this bug and ask eholk about the status of #627.