Comment 4 for bug 199860

Seeing the same thing. Attached a debugger, without debug symbols this is the best I can give you:

(gdb) where
#0 0x00007fcf35feefe6 in pthread_cond_signal@@GLIBC_2.3.2 ()
   from /lib/libpthread.so.0
#1 0x00007fcf2d553968 in ?? () from /usr/lib/libnspr4.so.0d
#2 0x00007fcf2d553c3d in PR_Unlock () from /usr/lib/libnspr4.so.0d
#3 0x00007fcf2ccbdd2d in ?? () from /usr/lib/xulrunner-1.9b3/libxul.so
#4 0x00007fcf2cc3d20e in ?? () from /usr/lib/xulrunner-1.9b3/libxul.so
#5 0x00007fcf2cc3deac in ?? () from /usr/lib/xulrunner-1.9b3/libxul.so
#6 0x00007fcf2ccbd4a5 in ?? () from /usr/lib/xulrunner-1.9b3/libxul.so
#7 0x00007fcf2ccbda05 in ?? () from /usr/lib/xulrunner-1.9b3/libxul.so
#8 0x00007fcf2ccbb94d in ?? () from /usr/lib/xulrunner-1.9b3/libxul.so
#9 0x00007fcf2cc901f4 in ?? () from /usr/lib/xulrunner-1.9b3/libxul.so
#10 0x00007fcf2cc09057 in ?? () from /usr/lib/xulrunner-1.9b3/libxul.so
#11 0x00007fcf2cbf6dfe in ?? () from /usr/lib/xulrunner-1.9b3/libxul.so
#12 0x00007fcf372a33b4 in g_main_context_dispatch ()
   from /usr/lib/libglib-2.0.so.0
#13 0x00007fcf372a66c5 in ?? () from /usr/lib/libglib-2.0.so.0
#14 0x00007fcf372a69e5 in g_main_loop_run () from /usr/lib/libglib-2.0.so.0
#15 0x00007fcf38b89d63 in gtk_main () from /usr/lib/libgtk-x11-2.0.so.0
#16 0x000000000041c120 in ?? ()
#17 0x00007fcf35ca01c4 in __libc_start_main () from /lib/libc.so.6
#18 0x000000000040dcb9 in ?? ()
#19 0x00007fff41d6b778 in ?? ()
#20 0x0000000000000000 in ?? ()

Attached a screenshot of the CPU usage. 50% because its a dual CPU box.

Seems to be spinning between the above and this:

(gdb) where
#0 0x00007fcf35feefe6 in pthread_cond_signal@@GLIBC_2.3.2 ()
   from /lib/libpthread.so.0
#1 0x00007fcf2d553968 in ?? () from /usr/lib/libnspr4.so.0d
#2 0x00007fcf2d553c3d in PR_Unlock () from /usr/lib/libnspr4.so.0d
#3 0x00007fcf2ccbdd2d in ?? () from /usr/lib/xulrunner-1.9b3/libxul.so
#4 0x00007fcf2cc3d20e in ?? () from /usr/lib/xulrunner-1.9b3/libxul.so
#5 0x00007fcf2cc3deac in ?? () from /usr/lib/xulrunner-1.9b3/libxul.so
#6 0x00007fcf2ccbd4a5 in ?? () from /usr/lib/xulrunner-1.9b3/libxul.so
#7 0x00007fcf2ccbda05 in ?? () from /usr/lib/xulrunner-1.9b3/libxul.so
#8 0x00007fcf2ccbb94d in ?? () from /usr/lib/xulrunner-1.9b3/libxul.so
#9 0x00007fcf2cc901f4 in ?? () from /usr/lib/xulrunner-1.9b3/libxul.so
#10 0x00007fcf2cc09057 in ?? () from /usr/lib/xulrunner-1.9b3/libxul.so
#11 0x00007fcf2cbf6dfe in ?? () from /usr/lib/xulrunner-1.9b3/libxul.so
#12 0x00007fcf372a33b4 in g_main_context_dispatch ()
   from /usr/lib/libglib-2.0.so.0
#13 0x00007fcf372a66c5 in ?? () from /usr/lib/libglib-2.0.so.0
#14 0x00007fcf372a69e5 in g_main_loop_run () from /usr/lib/libglib-2.0.so.0
#15 0x00007fcf38b89d63 in gtk_main () from /usr/lib/libgtk-x11-2.0.so.0
#16 0x000000000041c120 in ?? ()
#17 0x00007fcf35ca01c4 in __libc_start_main () from /lib/libc.so.6
#18 0x000000000040dcb9 in ?? ()
#19 0x00007fff41d6b778 in ?? ()
#20 0x0000000000000000 in ?? ()

Though I'm not particularly adept at gdb.

Its hard to reproduce, takes sometimes up to 5 minuts of clicking around and entering text into the search box to get it to do it.