diff options
| author | Andy Lutomirski <luto@amacapital.net> | 2014-09-05 15:13:53 -0700 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2014-09-08 14:13:59 -0700 |
| commit | fd143b210e685f0c4b37895f03fb79cd0555b00d (patch) | |
| tree | 6e05e277c6a9f6cffde189ef7375996813a4f231 | |
| parent | 81f49a8fd7088cfcb588d182eeede862c0e3303e (diff) | |
| download | tip-fd143b210e685f0c4b37895f03fb79cd0555b00d.tar.gz | |
x86, entry: Only call user_exit if TIF_NOHZ
The RCU context tracking code requires that arch code call
user_exit() on any entry into kernel code if TIF_NOHZ is set. This
patch adds a check for TIF_NOHZ and a comment to the syscall entry
tracing code.
The main purpose of this patch is to make the code easier to follow:
one can read the body of user_exit and of every function it calls
without finding any explanation of why it's called for traced
syscalls but not for untraced syscalls. This makes it clear when
user_exit() is necessary.
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/0b13e0e24ec0307d67ab7a23b58764f6b1270116.1409954077.git.luto@amacapital.net
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
| -rw-r--r-- | arch/x86/kernel/ptrace.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c index 39296d25708c75..bbf338a04a5d82 100644 --- a/arch/x86/kernel/ptrace.c +++ b/arch/x86/kernel/ptrace.c @@ -1449,7 +1449,12 @@ long syscall_trace_enter(struct pt_regs *regs) { long ret = 0; - user_exit(); + /* + * If TIF_NOHZ is set, we are required to call user_exit() before + * doing anything that could touch RCU. + */ + if (test_thread_flag(TIF_NOHZ)) + user_exit(); /* * If we stepped into a sysenter/syscall insn, it trapped in |