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author | Vegard Nossum <vegard.nossum@oracle.com> | 2015-12-18 23:28:53 +0300 |
---|---|---|
committer | Richard Weinberger <richard@nod.at> | 2016-01-10 23:49:47 +0300 |
commit | 0754fb298f2f2719f0393491d010d46cfb25d043 (patch) | |
tree | 50e373a0423f25e4707b198b7a5693e169b8cbad /arch | |
parent | 9f2dfda2f2f1c6181c3732c16b85c59ab2d195e0 (diff) | |
download | linux-0754fb298f2f2719f0393491d010d46cfb25d043.tar.xz |
uml: flush stdout before forking
I was seeing some really weird behaviour where piping UML's output
somewhere would cause output to get duplicated:
$ ./vmlinux | head -n 40
Checking that ptrace can change system call numbers...Core dump limits :
soft - 0
hard - NONE
OK
Checking syscall emulation patch for ptrace...Core dump limits :
soft - 0
hard - NONE
OK
Checking advanced syscall emulation patch for ptrace...Core dump limits :
soft - 0
hard - NONE
OK
Core dump limits :
soft - 0
hard - NONE
This is because these tests do a fork() which duplicates the non-empty
stdout buffer, then glibc flushes the duplicated buffer as each child
exits.
A simple workaround is to flush before forking.
Cc: stable@vger.kernel.org
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Diffstat (limited to 'arch')
-rw-r--r-- | arch/um/os-Linux/start_up.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/um/os-Linux/start_up.c b/arch/um/os-Linux/start_up.c index 47f1ff056a54..22a358ef1b0c 100644 --- a/arch/um/os-Linux/start_up.c +++ b/arch/um/os-Linux/start_up.c @@ -94,6 +94,8 @@ static int start_ptraced_child(void) { int pid, n, status; + fflush(stdout); + pid = fork(); if (pid == 0) ptrace_child(); |