gemvertexbuffer crashes on Intel after 2 rendering context creation when closing patch

gdbbacktrace

Program received signal SIGSEGV, Segmentation fault.
0xffffffffffffffff in ?? ()
(gdb) thread apply all bt

Thread 7 (Thread 0x7fffd8223700 (LWP 17836)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1  0x00007fffdbd397d3 in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so
#2  0x00007fffdbd39037 in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so
#3  0x00007ffff739e0a5 in start_thread (arg=0x7fffd8223700) at pthread_create.c:309
#4  0x00007ffff6ec784d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Thread 6 (Thread 0x7fffd8a24700 (LWP 17835)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1  0x00007fffdbd397d3 in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so
#2  0x00007fffdbd39037 in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so
#3  0x00007ffff739e0a5 in start_thread (arg=0x7fffd8a24700) at pthread_create.c:309
#4  0x00007ffff6ec784d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Thread 5 (Thread 0x7fffd9225700 (LWP 17834)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1  0x00007fffdbd397d3 in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so
#2  0x00007fffdbd39037 in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so
#3  0x00007ffff739e0a5 in start_thread (arg=0x7fffd9225700) at pthread_create.c:309
#4  0x00007ffff6ec784d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Thread 4 (Thread 0x7fffd9a26700 (LWP 17833)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1  0x00007fffdbd397d3 in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so
#2  0x00007fffdbd39037 in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so
#3  0x00007ffff739e0a5 in start_thread (arg=0x7fffd9a26700) at pthread_create.c:309
#4  0x00007ffff6ec784d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Thread 3 (Thread 0x7fffe06ea700 (LWP 17831)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1  0x00007ffff3804279 in freeze (this=0xc0ad50, this=0xc0ad50) at ThreadSemaphore.cpp:52
#2  gem::thread::Semaphore::freeze (this=<optimized out>) at ThreadSemaphore.cpp:74
#3  0x00007ffff38054a0 in gem::thread::WorkerThread::PIMPL::process (you=0xc028c0) at WorkerThread.cpp:117
#4  0x00007ffff739e0a5 in start_thread (arg=0x7fffe06ea700) at pthread_create.c:309
#5  0x00007ffff6ec784d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Thread 1 (Thread 0x7ffff7fb4780 (LWP 17823)):
#0  0xffffffffffffffff in ?? ()
#1  0x00007fffdb94c31d in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so
#2  0x00007fffdb8174fd in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so
#3  0x00007fffdb81c293 in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so
#4  0x00007ffff37ccc6b in gem::VertexBuffer::destroy (this=this@entry=0x2811050) at VertexBuffer.cpp:129
#5  0x00007ffff37ccca0 in gem::VertexBuffer::~VertexBuffer (this=0x2811050, __in_chrg=<optimized out>)
    at VertexBuffer.cpp:68
#6  0x00007ffff38b80a4 in gemvertexbuffer::~gemvertexbuffer (this=0x2810ea0, __in_chrg=<optimized out>)
    at gemvertexbuffer.cpp:60
#7  0x00007ffff38b8169 in gemvertexbuffer::~gemvertexbuffer (this=0x2810ea0, __in_chrg=<optimized out>)
    at gemvertexbuffer.cpp:62
#8  0x000000000046eac9 in pd_free ()
#9  0x000000000041815d in glist_delete ()
#10 0x0000000000413e38 in canvas_free ()
#11 0x000000000046eac9 in pd_free ()
#12 0x0000000000470a9d in pd_typedmess ()
#13 0x000000000047085c in pd_typedmess ()
#14 0x000000000047a2ec in binbuf_eval ()
#15 0x0000000000484d3c in socketreceiver_read ()
#16 0x000000000048405d in sys_domicrosleep.constprop ()
#17 0x0000000000480960 in m_mainloop ()
#18 0x00007ffff6deeec5 in __libc_start_main (main=0x412610 <main>, argc=8, argv=0x7fffffffde18, init=<optimized out>, 
    fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffffffde08) at libc-start.c:287
#19 0x000000000041263e in _start ()
(gdb)