diff options
author | Andy Lutomirski <luto@kernel.org> | 2015-10-05 17:48:23 -0700 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2015-10-09 09:41:13 +0200 |
commit | 39b48e575e92e31251b74b4b48cea2129cee90bd (patch) | |
tree | 0a57f6053546e0a191920e99415ad9e605231aeb /arch/x86/entry | |
parent | dd636071c3d8044c802b7a365e9934724a929530 (diff) | |
download | linux-39b48e575e92e31251b74b4b48cea2129cee90bd.tar.bz2 |
x86/entry: Split and inline prepare_exit_to_usermode()
GCC is unable to properly optimize functions that have a very
short likely case and a longer and register-heavier cold part --
it fails to sink all of the register saving and stack frame
setup code into the unlikely part.
Help it out with prepare_exit_to_usermode() by splitting it into
two parts and inline the hot part.
Saves 6-8 cycles for compat syscalls.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/9fc53eda4a5b924070952f12fa4ae3e477640a07.1444091585.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/entry')
-rw-r--r-- | arch/x86/entry/common.c | 43 |
1 files changed, 28 insertions, 15 deletions
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index d0874210d5b5..66ccbd664d4c 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -218,14 +218,12 @@ long syscall_trace_enter(struct pt_regs *regs) return syscall_trace_enter_phase2(regs, arch, phase1_result); } -/* Called with IRQs disabled. */ -__visible void prepare_exit_to_usermode(struct pt_regs *regs) -{ - if (IS_ENABLED(CONFIG_PROVE_LOCKING) && WARN_ON(!irqs_disabled())) - local_irq_disable(); - - lockdep_sys_exit(); +#define EXIT_TO_USERMODE_LOOP_FLAGS \ + (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE | \ + _TIF_NEED_RESCHED | _TIF_USER_RETURN_NOTIFY) +static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags) +{ /* * In order to return to user mode, we need to have IRQs off with * none of _TIF_SIGPENDING, _TIF_NOTIFY_RESUME, _TIF_USER_RETURN_NOTIFY, @@ -235,14 +233,6 @@ __visible void prepare_exit_to_usermode(struct pt_regs *regs) * work to clear some of the flags can sleep. */ while (true) { - u32 cached_flags = - READ_ONCE(pt_regs_to_thread_info(regs)->flags); - - if (!(cached_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | - _TIF_UPROBE | _TIF_NEED_RESCHED | - _TIF_USER_RETURN_NOTIFY))) - break; - /* We have work to do. */ local_irq_enable(); @@ -266,7 +256,30 @@ __visible void prepare_exit_to_usermode(struct pt_regs *regs) /* Disable IRQs and retry */ local_irq_disable(); + + cached_flags = READ_ONCE(pt_regs_to_thread_info(regs)->flags); + + if (!(cached_flags & EXIT_TO_USERMODE_LOOP_FLAGS)) + break; + } +} + +/* Called with IRQs disabled. */ +__visible inline void prepare_exit_to_usermode(struct pt_regs *regs) +{ + u32 cached_flags; + + if (IS_ENABLED(CONFIG_PROVE_LOCKING) && WARN_ON(!irqs_disabled())) + local_irq_disable(); + + lockdep_sys_exit(); + + cached_flags = + READ_ONCE(pt_regs_to_thread_info(regs)->flags); + + if (unlikely(cached_flags & EXIT_TO_USERMODE_LOOP_FLAGS)) + exit_to_usermode_loop(regs, cached_flags); user_enter(); } |