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authorHaavard Skinnemoen <hskinnemoen@atmel.com>2008-02-27 14:04:29 +0100
committerHaavard Skinnemoen <hskinnemoen@atmel.com>2008-02-27 14:23:53 +0100
commit325d6f5593b40b5a48cf4ade74c01681f2ff6044 (patch)
treefacb22a7deb7b6c9ce2bdaf07bcc4ac3bd8d21b5 /arch/avr32/kernel
parentd45ad06273f797f6239b97fd9962ecd81eec847f (diff)
downloadop-kernel-dev-325d6f5593b40b5a48cf4ade74c01681f2ff6044.zip
op-kernel-dev-325d6f5593b40b5a48cf4ade74c01681f2ff6044.tar.gz
avr32: Fix OCD refcounting bug
Iff the parent has TIF_DEBUG set, _and_ clone_flags includes CLONE_PTRACE we should set the TIF_DEBUG flag for the child and increment the ocd refcount. Otherwise, the TIF_DEBUG flag must be unset. Currently, the child inherits TIF_DEBUG from the parent before copy_thread is called, so TIF_DEBUG may be already be set before we determine whether the child is supposed to inherit debugging capabilities from the parent or not. This means that ocd_enable() won't increment the refcount, because TIF_DEBUG is already set, and that TIF_DEBUG will be set for processes that aren't being debugged. This leads to a refcounting asymmetry, which may show up as ------------[ cut here ]------------ Badness at arch/avr32/kernel/ocd.c:73 PC is at ocd_disable+0x34/0x60 LR is at put_lock_stats+0xa/0x20 as reported by David Brownell. Happens when strace'ing a process that forks a new child process, e.g. "strace mount -tjffs2 mtd1 /mnt", and subsequently killing the child process (e.g. "umount /mnt".) Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Diffstat (limited to 'arch/avr32/kernel')
-rw-r--r--arch/avr32/kernel/process.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/avr32/kernel/process.c b/arch/avr32/kernel/process.c
index faf8d0e..7f4af0b 100644
--- a/arch/avr32/kernel/process.c
+++ b/arch/avr32/kernel/process.c
@@ -348,6 +348,7 @@ int copy_thread(int nr, unsigned long clone_flags, unsigned long usp,
p->thread.cpu_context.ksp = (unsigned long)childregs;
p->thread.cpu_context.pc = (unsigned long)ret_from_fork;
+ clear_tsk_thread_flag(p, TIF_DEBUG);
if ((clone_flags & CLONE_PTRACE) && test_thread_flag(TIF_DEBUG))
ocd_enable(p);
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