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x86/entry: Rename idtentry_enter/exit_cond_rcu() to idtentry_enter/exit()

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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.

No functional change -- it's pure refactoring.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/247fc67685263e0b673e1d7f808182d28ff80359.1593795633.git.luto@kernel.org
This commit is contained in:
Andy Lutomirski
2020-07-03 10:02:58 -07:00
committed by Thomas Gleixner
parent dcb7fd82c7
commit b037b09b90
5 changed files with 53 additions and 43 deletions
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50
arch/x86/entry/common.c
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@@ -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 */