Red Hat Bugzilla – Bug 113892
System freezes when strace attaches to XFree86
Last modified: 2007-11-30 17:10:35 EST
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User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4.1)
Description of problem:
While trying to determine what XFree86 was doing, I ran 'strace -f -p
<pid>' on it. I got a few lines of unsurprising output and then the
machine froze up. I connected to the machine remotely and kill -9 X,
which returned the machine to a usable state.
I can reproduce this at will on several machines, and will include
magic-sysrq task list output from a machine in the frozen state.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. start X windows
2. run 'strace -f -p <pid>', where <pid> is the PID of the X binary
3. watch the machine freeze after spitting out some output.
4. if the machine doesn't freeze on its own, move the mouse.
Actual Results: the machine is unresponsive, except for network
Expected Results: strace should have shown process output until I hit
ctrl-c. the machine
shouldn't have frozen.
Created attachment 97111 [details]
magic sysrq output of a machine in the frozen state
Created attachment 97112 [details]
magic sysrq task list output, round 2
When attempting to debug the X server, or any of its modules,
you must not run the debugging software from within the X server
you are attempting to debug/strace/etc. You must run the X server
alone, and run the debugger/strace/etc. from a remote network
session or serial console, or other access mechanism.
Closing as NOTABUG.