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authorLinus Torvalds <torvalds@linux-foundation.org>2020-06-28 10:29:38 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-28 10:29:38 -0700
commitc141b30e9960e81455ad9c3658c079051eea7e2d (patch)
tree4940596fa19d57c32f2f88a3037780bdb6c17db6 /kernel
parent7ecb59a56666506ebb1197f89ca7d587bd83309e (diff)
parentb58e733fd774f3f4b49d9e7640d172a57e35200e (diff)
Merge tag 'rcu_urgent_for_5.8_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull RCU-vs-KCSAN fixes from Borislav Petkov: "A single commit that uses "arch_" atomic operations to avoid the instrumentation that comes with the non-"arch_" versions. In preparation for that commit, it also has another commit that makes these "arch_" atomic operations available to generic code. Without these commits, KCSAN uses can see pointless errors" * tag 'rcu_urgent_for_5.8_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: rcu: Fixup noinstr warnings locking/atomics: Provide the arch_atomic_ interface to generic code
Diffstat (limited to 'kernel')
-rw-r--r--kernel/rcu/tree.c32
1 files changed, 25 insertions, 7 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index c716eadc7617..6c6569e0586c 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -250,7 +250,7 @@ static noinstr void rcu_dynticks_eqs_enter(void)
* next idle sojourn.
*/
rcu_dynticks_task_trace_enter(); // Before ->dynticks update!
- seq = atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
+ seq = arch_atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
// RCU is no longer watching. Better be in extended quiescent state!
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
(seq & RCU_DYNTICK_CTRL_CTR));
@@ -274,13 +274,13 @@ static noinstr void rcu_dynticks_eqs_exit(void)
* and we also must force ordering with the next RCU read-side
* critical section.
*/
- seq = atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
+ seq = arch_atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
// RCU is now watching. Better not be in an extended quiescent state!
rcu_dynticks_task_trace_exit(); // After ->dynticks update!
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
!(seq & RCU_DYNTICK_CTRL_CTR));
if (seq & RCU_DYNTICK_CTRL_MASK) {
- atomic_andnot(RCU_DYNTICK_CTRL_MASK, &rdp->dynticks);
+ arch_atomic_andnot(RCU_DYNTICK_CTRL_MASK, &rdp->dynticks);
smp_mb__after_atomic(); /* _exit after clearing mask. */
}
}
@@ -313,7 +313,7 @@ static __always_inline bool rcu_dynticks_curr_cpu_in_eqs(void)
{
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
- return !(atomic_read(&rdp->dynticks) & RCU_DYNTICK_CTRL_CTR);
+ return !(arch_atomic_read(&rdp->dynticks) & RCU_DYNTICK_CTRL_CTR);
}
/*
@@ -633,6 +633,10 @@ static noinstr void rcu_eqs_enter(bool user)
do_nocb_deferred_wakeup(rdp);
rcu_prepare_for_idle();
rcu_preempt_deferred_qs(current);
+
+ // instrumentation for the noinstr rcu_dynticks_eqs_enter()
+ instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks));
+
instrumentation_end();
WRITE_ONCE(rdp->dynticks_nesting, 0); /* Avoid irq-access tearing. */
// RCU is watching here ...
@@ -692,6 +696,7 @@ noinstr void rcu_nmi_exit(void)
{
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
+ instrumentation_begin();
/*
* Check for ->dynticks_nmi_nesting underflow and bad ->dynticks.
* (We are exiting an NMI handler, so RCU better be paying attention
@@ -705,7 +710,6 @@ noinstr void rcu_nmi_exit(void)
* leave it in non-RCU-idle state.
*/
if (rdp->dynticks_nmi_nesting != 1) {
- instrumentation_begin();
trace_rcu_dyntick(TPS("--="), rdp->dynticks_nmi_nesting, rdp->dynticks_nmi_nesting - 2,
atomic_read(&rdp->dynticks));
WRITE_ONCE(rdp->dynticks_nmi_nesting, /* No store tearing. */
@@ -714,13 +718,15 @@ noinstr void rcu_nmi_exit(void)
return;
}
- instrumentation_begin();
/* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0, atomic_read(&rdp->dynticks));
WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */
if (!in_nmi())
rcu_prepare_for_idle();
+
+ // instrumentation for the noinstr rcu_dynticks_eqs_enter()
+ instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks));
instrumentation_end();
// RCU is watching here ...
@@ -838,6 +844,10 @@ static void noinstr rcu_eqs_exit(bool user)
rcu_dynticks_eqs_exit();
// ... but is watching here.
instrumentation_begin();
+
+ // instrumentation for the noinstr rcu_dynticks_eqs_exit()
+ instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks));
+
rcu_cleanup_after_idle();
trace_rcu_dyntick(TPS("End"), rdp->dynticks_nesting, 1, atomic_read(&rdp->dynticks));
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
@@ -983,13 +993,21 @@ noinstr void rcu_nmi_enter(void)
if (!in_nmi())
rcu_cleanup_after_idle();
+ instrumentation_begin();
+ // instrumentation for the noinstr rcu_dynticks_curr_cpu_in_eqs()
+ instrument_atomic_read(&rdp->dynticks, sizeof(rdp->dynticks));
+ // instrumentation for the noinstr rcu_dynticks_eqs_exit()
+ instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks));
+
incby = 1;
} else if (!in_nmi()) {
instrumentation_begin();
rcu_irq_enter_check_tick();
instrumentation_end();
+ } else {
+ instrumentation_begin();
}
- instrumentation_begin();
+
trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="),
rdp->dynticks_nmi_nesting,
rdp->dynticks_nmi_nesting + incby, atomic_read(&rdp->dynticks));