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Date: Fri, 3 Jul 2020 10:02:58 -0700
From: Andy Lutomirski <luto@...nel.org>
To: x86@...nel.org
Cc: Andrew Cooper <andrew.cooper3@...rix.com>,
Juergen Gross <jgross@...e.com>,
LKML <linux-kernel@...r.kernel.org>,
Andy Lutomirski <luto@...nel.org>
Subject: [PATCH entry v2 6/6] x86/entry: Rename idtentry_enter/exit_cond_rcu() to idtentry_enter/exit()
They were originally called _cond_rcu because they were special
versions with conditional RCU handling. Now they're the standard
entry and exit path, so the _cond_rcu part is just confusing. Drop
it.
Also change the signature to make them more extensible and more
foolproof.
This patch makes no functional change -- it's pure refactoring.
Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
arch/x86/entry/common.c | 50 ++++++++++++++++++---------------
arch/x86/include/asm/idtentry.h | 28 ++++++++++--------
arch/x86/kernel/kvm.c | 6 ++--
arch/x86/kernel/traps.c | 6 ++--
arch/x86/mm/fault.c | 6 ++--
kernel/time/tick-sched.c | 1 +
6 files changed, 54 insertions(+), 43 deletions(-)
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index e83b3f14897c..0521546022cb 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -559,8 +559,7 @@ SYSCALL_DEFINE0(ni_syscall)
}
/**
- * idtentry_enter_cond_rcu - Handle state tracking on idtentry with conditional
- * RCU handling
+ * idtentry_enter - Handle state tracking on ordinary idtentries
* @regs: Pointer to pt_regs of interrupted context
*
* Invokes:
@@ -572,6 +571,9 @@ SYSCALL_DEFINE0(ni_syscall)
* - The hardirq tracer to keep the state consistent as low level ASM
* entry disabled interrupts.
*
+ * As a precondition, this requires that the entry came from user mode,
+ * idle, or a kernel context in which RCU is watching.
+ *
* For kernel mode entries RCU handling is done conditional. If RCU is
* watching then the only RCU requirement is to check whether the tick has
* to be restarted. If RCU is not watching then rcu_irq_enter() has to be
@@ -585,18 +587,21 @@ SYSCALL_DEFINE0(ni_syscall)
* establish the proper context for NOHZ_FULL. Otherwise scheduling on exit
* would not be possible.
*
- * Returns: True if RCU has been adjusted on a kernel entry
- * False otherwise
+ * Returns: An opaque object that must be passed to idtentry_exit()
*
- * The return value must be fed into the rcu_exit argument of
- * idtentry_exit_cond_rcu().
+ * The return value must be fed into the state argument of
+ * idtentry_exit().
*/
-bool noinstr idtentry_enter_cond_rcu(struct pt_regs *regs)
+idtentry_state_t noinstr idtentry_enter(struct pt_regs *regs)
{
+ idtentry_state_t ret = {
+ .exit_rcu = false,
+ };
+
if (user_mode(regs)) {
check_user_regs(regs);
enter_from_user_mode();
- return false;
+ return ret;
}
/*
@@ -634,7 +639,8 @@ bool noinstr idtentry_enter_cond_rcu(struct pt_regs *regs)
trace_hardirqs_off_finish();
instrumentation_end();
- return true;
+ ret.exit_rcu = true;
+ return ret;
}
/*
@@ -649,7 +655,7 @@ bool noinstr idtentry_enter_cond_rcu(struct pt_regs *regs)
trace_hardirqs_off();
instrumentation_end();
- return false;
+ return ret;
}
static void idtentry_exit_cond_resched(struct pt_regs *regs, bool may_sched)
@@ -667,10 +673,9 @@ static void idtentry_exit_cond_resched(struct pt_regs *regs, bool may_sched)
}
/**
- * idtentry_exit_cond_rcu - Handle return from exception with conditional RCU
- * handling
+ * idtentry_exit - Handle return from exception that used idtentry_enter()
* @regs: Pointer to pt_regs (exception entry regs)
- * @rcu_exit: Invoke rcu_irq_exit() if true
+ * @state: Return value from matching call to idtentry_enter()
*
* Depending on the return target (kernel/user) this runs the necessary
* preemption and work checks if possible and reguired and returns to
@@ -679,10 +684,10 @@ static void idtentry_exit_cond_resched(struct pt_regs *regs, bool may_sched)
* This is the last action before returning to the low level ASM code which
* just needs to return to the appropriate context.
*
- * Counterpart to idtentry_enter_cond_rcu(). The return value of the entry
- * function must be fed into the @rcu_exit argument.
+ * Counterpart to idtentry_enter(). The return value of the entry
+ * function must be fed into the @state argument.
*/
-void noinstr idtentry_exit_cond_rcu(struct pt_regs *regs, bool rcu_exit)
+void noinstr idtentry_exit(struct pt_regs *regs, idtentry_state_t state)
{
lockdep_assert_irqs_disabled();
@@ -695,7 +700,7 @@ void noinstr idtentry_exit_cond_rcu(struct pt_regs *regs, bool rcu_exit)
* carefully and needs the same ordering of lockdep/tracing
* and RCU as the return to user mode path.
*/
- if (rcu_exit) {
+ if (state.exit_rcu) {
instrumentation_begin();
/* Tell the tracer that IRET will enable interrupts */
trace_hardirqs_on_prepare();
@@ -714,7 +719,7 @@ void noinstr idtentry_exit_cond_rcu(struct pt_regs *regs, bool rcu_exit)
* IRQ flags state is correct already. Just tell RCU if it
* was not watching on entry.
*/
- if (rcu_exit)
+ if (state.exit_rcu)
rcu_irq_exit();
}
}
@@ -800,9 +805,10 @@ static void __xen_pv_evtchn_do_upcall(void)
__visible noinstr void xen_pv_evtchn_do_upcall(struct pt_regs *regs)
{
struct pt_regs *old_regs;
- bool inhcall, rcu_exit;
+ bool inhcall;
+ idtentry_state_t state;
- rcu_exit = idtentry_enter_cond_rcu(regs);
+ state = idtentry_enter(regs);
old_regs = set_irq_regs(regs);
instrumentation_begin();
@@ -812,13 +818,13 @@ __visible noinstr void xen_pv_evtchn_do_upcall(struct pt_regs *regs)
set_irq_regs(old_regs);
inhcall = get_and_clear_inhcall();
- if (inhcall && !WARN_ON_ONCE(rcu_exit)) {
+ if (inhcall && !WARN_ON_ONCE(state.exit_rcu)) {
instrumentation_begin();
idtentry_exit_cond_resched(regs, true);
instrumentation_end();
restore_inhcall(inhcall);
} else {
- idtentry_exit_cond_rcu(regs, rcu_exit);
+ idtentry_exit(regs, state);
}
}
#endif /* CONFIG_XEN_PV */
diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index eeac6dc2adaa..7227225cf45d 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -13,8 +13,12 @@
void idtentry_enter_user(struct pt_regs *regs);
void idtentry_exit_user(struct pt_regs *regs);
-bool idtentry_enter_cond_rcu(struct pt_regs *regs);
-void idtentry_exit_cond_rcu(struct pt_regs *regs, bool rcu_exit);
+typedef struct idtentry_state {
+ bool exit_rcu;
+} idtentry_state_t;
+
+idtentry_state_t idtentry_enter(struct pt_regs *regs);
+void idtentry_exit(struct pt_regs *regs, idtentry_state_t state);
/**
* DECLARE_IDTENTRY - Declare functions for simple IDT entry points
@@ -54,12 +58,12 @@ static __always_inline void __##func(struct pt_regs *regs); \
\
__visible noinstr void func(struct pt_regs *regs) \
{ \
- bool rcu_exit = idtentry_enter_cond_rcu(regs); \
+ idtentry_state_t state = idtentry_enter(regs); \
\
instrumentation_begin(); \
__##func (regs); \
instrumentation_end(); \
- idtentry_exit_cond_rcu(regs, rcu_exit); \
+ idtentry_exit(regs, state); \
} \
\
static __always_inline void __##func(struct pt_regs *regs)
@@ -101,12 +105,12 @@ static __always_inline void __##func(struct pt_regs *regs, \
__visible noinstr void func(struct pt_regs *regs, \
unsigned long error_code) \
{ \
- bool rcu_exit = idtentry_enter_cond_rcu(regs); \
+ idtentry_state_t state = idtentry_enter(regs); \
\
instrumentation_begin(); \
__##func (regs, error_code); \
instrumentation_end(); \
- idtentry_exit_cond_rcu(regs, rcu_exit); \
+ idtentry_exit(regs, state); \
} \
\
static __always_inline void __##func(struct pt_regs *regs, \
@@ -199,7 +203,7 @@ static __always_inline void __##func(struct pt_regs *regs, u8 vector); \
__visible noinstr void func(struct pt_regs *regs, \
unsigned long error_code) \
{ \
- bool rcu_exit = idtentry_enter_cond_rcu(regs); \
+ idtentry_state_t state = idtentry_enter(regs); \
\
instrumentation_begin(); \
irq_enter_rcu(); \
@@ -207,7 +211,7 @@ __visible noinstr void func(struct pt_regs *regs, \
__##func (regs, (u8)error_code); \
irq_exit_rcu(); \
instrumentation_end(); \
- idtentry_exit_cond_rcu(regs, rcu_exit); \
+ idtentry_exit(regs, state); \
} \
\
static __always_inline void __##func(struct pt_regs *regs, u8 vector)
@@ -241,7 +245,7 @@ static void __##func(struct pt_regs *regs); \
\
__visible noinstr void func(struct pt_regs *regs) \
{ \
- bool rcu_exit = idtentry_enter_cond_rcu(regs); \
+ idtentry_state_t state = idtentry_enter(regs); \
\
instrumentation_begin(); \
irq_enter_rcu(); \
@@ -249,7 +253,7 @@ __visible noinstr void func(struct pt_regs *regs) \
run_on_irqstack_cond(__##func, regs, regs); \
irq_exit_rcu(); \
instrumentation_end(); \
- idtentry_exit_cond_rcu(regs, rcu_exit); \
+ idtentry_exit(regs, state); \
} \
\
static noinline void __##func(struct pt_regs *regs)
@@ -270,7 +274,7 @@ static __always_inline void __##func(struct pt_regs *regs); \
\
__visible noinstr void func(struct pt_regs *regs) \
{ \
- bool rcu_exit = idtentry_enter_cond_rcu(regs); \
+ idtentry_state_t state = idtentry_enter(regs); \
\
instrumentation_begin(); \
__irq_enter_raw(); \
@@ -278,7 +282,7 @@ __visible noinstr void func(struct pt_regs *regs) \
__##func (regs); \
__irq_exit_raw(); \
instrumentation_end(); \
- idtentry_exit_cond_rcu(regs, rcu_exit); \
+ idtentry_exit(regs, state); \
} \
\
static __always_inline void __##func(struct pt_regs *regs)
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index df63786e7bfa..3f78482d9496 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -233,7 +233,7 @@ EXPORT_SYMBOL_GPL(kvm_read_and_reset_apf_flags);
noinstr bool __kvm_handle_async_pf(struct pt_regs *regs, u32 token)
{
u32 reason = kvm_read_and_reset_apf_flags();
- bool rcu_exit;
+ idtentry_state_t state;
switch (reason) {
case KVM_PV_REASON_PAGE_NOT_PRESENT:
@@ -243,7 +243,7 @@ noinstr bool __kvm_handle_async_pf(struct pt_regs *regs, u32 token)
return false;
}
- rcu_exit = idtentry_enter_cond_rcu(regs);
+ state = idtentry_enter(regs);
instrumentation_begin();
/*
@@ -264,7 +264,7 @@ noinstr bool __kvm_handle_async_pf(struct pt_regs *regs, u32 token)
}
instrumentation_end();
- idtentry_exit_cond_rcu(regs, rcu_exit);
+ idtentry_exit(regs, state);
return true;
}
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 6ed8cc5fbe8f..de75e531cdd2 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -218,7 +218,7 @@ static inline void handle_invalid_op(struct pt_regs *regs)
DEFINE_IDTENTRY_RAW(exc_invalid_op)
{
- bool rcu_exit;
+ idtentry_state_t state;
/*
* Handle BUG/WARN like NMIs instead of like normal idtentries:
@@ -251,11 +251,11 @@ DEFINE_IDTENTRY_RAW(exc_invalid_op)
*/
}
- rcu_exit = idtentry_enter_cond_rcu(regs);
+ state = idtentry_enter(regs);
instrumentation_begin();
handle_invalid_op(regs);
instrumentation_end();
- idtentry_exit_cond_rcu(regs, rcu_exit);
+ idtentry_exit(regs, state);
}
DEFINE_IDTENTRY(exc_coproc_segment_overrun)
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 1ead568c0101..5e41949453cc 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1377,7 +1377,7 @@ handle_page_fault(struct pt_regs *regs, unsigned long error_code,
DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
{
unsigned long address = read_cr2();
- bool rcu_exit;
+ idtentry_state_t state;
prefetchw(¤t->mm->mmap_lock);
@@ -1412,11 +1412,11 @@ DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
* code reenabled RCU to avoid subsequent wreckage which helps
* debugability.
*/
- rcu_exit = idtentry_enter_cond_rcu(regs);
+ state = idtentry_enter(regs);
instrumentation_begin();
handle_page_fault(regs, error_code, address);
instrumentation_end();
- idtentry_exit_cond_rcu(regs, rcu_exit);
+ idtentry_exit(regs, state);
}
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 3e2dc9b8858c..6aa0daca0dd2 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -921,6 +921,7 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
(local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK)) {
pr_warn("NOHZ: local_softirq_pending %02x\n",
(unsigned int) local_softirq_pending());
+ WARN_ON_ONCE(1);
ratelimit++;
}
return false;
--
2.25.4
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