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authorAndy Lutomirski <luto@amacapital.net>2014-09-05 15:13:53 -0700
committerH. Peter Anvin <hpa@linux.intel.com>2014-09-08 14:13:59 -0700
commitfd143b210e685f0c4b37895f03fb79cd0555b00d (patch)
tree6e05e277c6a9f6cffde189ef7375996813a4f231 /arch/x86/kernel/ptrace.c
parent81f49a8fd7088cfcb588d182eeede862c0e3303e (diff)
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>
Diffstat (limited to 'arch/x86/kernel/ptrace.c')
-rw-r--r--arch/x86/kernel/ptrace.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 39296d25708..bbf338a04a5 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