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| author | Vegard Nossum <vegard.nossum@oracle.com> | 2015-12-18 21:28:53 +0100 |
|---|---|---|
| committer | Sasha Levin <sasha.levin@oracle.com> | 2016-02-03 14:01:45 -0500 |
| commit | 498b346868790663ef443951bb06a30a57b64b32 (patch) | |
| tree | b7f221bddb839ffc51a49fbc0aa7f752416c4980 /arch/um | |
| parent | 4e623240d3054ca29fbb294d15a24b2ed971a413 (diff) | |
| download | linux-exynos-498b346868790663ef443951bb06a30a57b64b32.tar.gz linux-exynos-498b346868790663ef443951bb06a30a57b64b32.tar.bz2 linux-exynos-498b346868790663ef443951bb06a30a57b64b32.zip | |
uml: flush stdout before forking
[ Upstream commit 0754fb298f2f2719f0393491d010d46cfb25d043 ]
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>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Diffstat (limited to 'arch/um')
| -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(); |