Red Hat Bugzilla – Bug 455078
[4.7] strace -f fails to follow vfork() processes on ia64 - hangs instead - possible kernel bug?
Last modified: 2012-06-14 16:44:44 EDT
+++ This bug was initially created as a clone of Bug #452501 +++ `strace -f ./vfork' hangs on ia64. (`-F' is not needed on GNU/Linux, `-f' is enough to trace vfork(2).) RHEL4-U7-re20080711.0 kernel-2.6.9-78.EL.ia64 strace-4.5.16-1.el4.2.ia64 -- Additional comment from vmayatsk@redhat.com on 2008-06-26 10:35 EST -- This is because IA64 uses clone() instead of vfork(). I played a bit with strace sources and found that function setbpt() (file util.c) has flag CLONE_VFORK set in tcp->inst[0] for the case of SYS_clone/clone2, but hasn't it in the case of SYS_fork/vfork. When I manually remove CLONE_VFORK from inst[0] (case SYS_clone), strace -f on IA64 works just like as on x86_64. When I manually add 0x4000 (CLONE_VFORK) to arg0 (case SYS_fork) it hangs on x86_64 just like as on IA64. I'm not an expert in strace, but seems it's a bug in strace utility. -- Additional comment from jan.kratochvil@redhat.com on 2008-07-08 14:15 EST -- [...] The ia64 threads fix is unrelated but posted here: http://sourceforge.net/mailarchive/message.php?msg_name=20080630164049.GA19501%40host0.dyn.jankratochvil.net ############################################################################### RHEL4-U7-re20080711.0 ia64 kernel-2.6.9-78.EL.ia64 strace-4.5.16-1.el4.2.ia64 $ strace -f ./vfork ... clone(Process 16684 attached (waiting for parent) [ hang ] RHEL4-U7-re20080711.0 ia64 kernel-2.6.9-78.EL.ia64 strace-4.5.16-1.el4.2.ia64 + the patch above [ This trace was copied from RHEL-5.2 Bug 452501 but it looks the same. ] $ ./strace -f ./vfork ... clone(Process 20396 attached child_stack=0, flags=CLONE_VM|CLONE_VFORK|SIGCHLD) = 20396 [pid 20395] getpid() = 20395 ... [pid 20395] write(1, "20396 pid=20395\n", 1620396 pid=20395 ) = 16 ... [pid 20395] nanosleep({1, 0}, <unfinished ...> [pid 20396] write(1, "0 pid=20395\n", 120 pid=20395 ) = 12 ... [pid 20396] nanosleep({1, 0}, <unfinished ...> [pid 20395] <... nanosleep resumed> {1, 0}) = 0 [pid 20395] execve("/bin/true", ["/bin/true"...], [/* 47 vars */] <unfinished ...> [pid 20396] <... nanosleep resumed> {1, 0}) = 0 [pid 20396] execve("/bin/true", ["/bin/true"...], [/* 47 vars */]) = 1 [pid 20395] <... execve resumed> ) = 1 ... [pid 20395] fstat(3, <unfinished ...> [pid 20396] exit_group(0) = ? Process 20396 detached <... fstat resumed> {st_mode=S_IFREG|0644, st_size=58727440, ...}) = 0 --- SIGCHLD (Child exited) @ a000000000010621 (4fac) --- mmap(NULL, 58727440, PROT_READ, MAP_PRIVATE, 3, 0) = 0x2000000000308000 close(3) = 0 close(1) = 0 exit_group(0) = ?
Created attachment 311618 [details] Simple vfork(2) testcase.
Have no RHEL4 ia64 machine at the moment to experiment with, but on RHEL5: strace-4.5.16-1.el5.1 - exhibits this bug, strace-4.5.16-1.el5_2.2 - does not. Just FYI.
A few more data points: On RHEL4-U7, installed version of strace is strace-4.5.16-1.el4.2 and it exhibits the bug. I just tested that last upstream release - strace-4.5.18 - can be successfully built on RHEL4-U7 and it does not exhibit this bug.
This request was evaluated by Red Hat Product Management for inclusion, but this component is not scheduled to be updated in the current Red Hat Enterprise Linux release. If you would like this request to be reviewed for the next minor release, ask your support representative to set the next rhel-x.y flag to "?".
Created attachment 347532 [details] Proposed backported fix from 4.5.17 Tested to work with the testcase attached by Jan on ia64 Red Hat Enterprise Linux AS release 4 (Nahant Update 8)
That backport looks fine to me.