Commit-ID: fd143b210e685f0c4b37895f03fb79cd0555b00d Gitweb: http://git.kernel.org/tip/fd143b210e685f0c4b37895f03fb79cd0555b00d Author: Andy Lutomirski <l...@amacapital.net> AuthorDate: Fri, 5 Sep 2014 15:13:53 -0700 Committer: H. Peter Anvin <h...@linux.intel.com> CommitDate: Mon, 8 Sep 2014 14:13:59 -0700
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 <fweis...@gmail.com> Signed-off-by: Andy Lutomirski <l...@amacapital.net> Link: http://lkml.kernel.org/r/0b13e0e24ec0307d67ab7a23b58764f6b1270116.1409954077.git.l...@amacapital.net Signed-off-by: H. Peter Anvin <h...@linux.intel.com> --- arch/x86/kernel/ptrace.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c index 39296d2..bbf338a 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
