With latest -tip I get this bug:
[ 49.439988] in_atomic():0, irqs_disabled():1
[ 49.440118] INFO: lockdep is turned off.
[ 49.440118] Pid: 2814, comm: modprobe Tainted: G W 2.6.27-rc7 #4
[ 49.440118] [<c01215e1>] __might_sleep+0xe1/0x120
[ 49.440118] [<c01148ea>] ftrace_modify_code+0x2a/0xd0
[ 49.440118] [<c01148a2>] ? ftrace_test_p6nop+0x0/0xa
[ 49.440118] [<c016e80e>] __ftrace_update_code+0xfe/0x2f0
[ 49.440118] [<c01148a2>] ? ftrace_test_p6nop+0x0/0xa
[ 49.440118] [<c016f190>] ftrace_convert_nops+0x50/0x80
[ 49.440118] [<c016f1d6>] ftrace_init_module+0x16/0x20
[ 49.440118] [<c015498b>] load_module+0x185b/0x1d30
[ 49.440118] [<c01767a0>] ? find_get_page+0x0/0xf0
[ 49.440118] [<c02463c0>] ? sprintf+0x0/0x30
[ 49.440118] [<c034e012>] ? mutex_lock_interruptible_nested+0x1f2/0x350
[ 49.440118] [<c0154eb3>] sys_init_module+0x53/0x1b0
[ 49.440118] [<c0352340>] ? do_page_fault+0x0/0x740
[ 49.440118] [<c0104012>] syscall_call+0x7/0xb
[ 49.440118] =======================
It is because ftrace_modify_code() calls copy_to_user and
copy_from_user.
These functions have been inserted after guessing that there
couldn't be any race condition but copy_[to/from]_user might
sleep and __ftrace_update_code is called with local_irq_saved.
These function have been inserted since this commit:
d5e92e8978fd2574e415dc2792c5eb592978243d:
"ftrace: x86 use copy from user function"
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
ac2b86fdef