srcu: Debug NMI safety even on archs that don't require it

Currently the NMI safety debugging is only performed on architectures
that don't support NMI-safe this_cpu_inc().

Reorder the code so that other architectures like x86 also detect bad
uses.

[ paulmck: Apply kernel test robot, Stephen Rothwell, and Zqiang feedback. ]

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index 1a7840c1b87ad66d82df192cb517e67d9af496a8..f0814ffca34bbba4497ad17e5a7724c43d669b13 100644 (file)
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -65,14 +65,14 @@ unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp);
 bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie);
 
 #ifdef CONFIG_NEED_SRCU_NMI_SAFE
-int __srcu_read_lock_nmisafe(struct srcu_struct *ssp, bool chknmisafe) __acquires(ssp);
-void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx, bool chknmisafe) __releases(ssp);
+int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp);
+void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) __releases(ssp);
 #else
-static inline int __srcu_read_lock_nmisafe(struct srcu_struct *ssp, bool chknmisafe)
+static inline int __srcu_read_lock_nmisafe(struct srcu_struct *ssp)
 {
        return __srcu_read_lock(ssp);
 }
-static inline void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx, bool chknmisafe)
+static inline void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx)
 {
        __srcu_read_unlock(ssp, idx);
 }
@@ -118,6 +118,18 @@ static inline int srcu_read_lock_held(const struct srcu_struct *ssp)
 
 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
+#define SRCU_NMI_UNKNOWN       0x0
+#define SRCU_NMI_UNSAFE                0x1
+#define SRCU_NMI_SAFE          0x2
+
+#if defined(CONFIG_PROVE_RCU) && defined(CONFIG_TREE_SRCU)
+void srcu_check_nmi_safety(struct srcu_struct *ssp, bool nmi_safe);
+#else
+static inline void srcu_check_nmi_safety(struct srcu_struct *ssp,
+                                        bool nmi_safe) { }
+#endif
+
+
 /**
  * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing
  * @p: the pointer to fetch and protect for later dereferencing
@@ -175,6 +187,7 @@ static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp)
 {
        int retval;
 
+       srcu_check_nmi_safety(ssp, false);
        retval = __srcu_read_lock(ssp);
        rcu_lock_acquire(&(ssp)->dep_map);
        return retval;
@@ -191,10 +204,8 @@ static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp
 {
        int retval;
 
-       if (IS_ENABLED(CONFIG_NEED_SRCU_NMI_SAFE))
-               retval = __srcu_read_lock_nmisafe(ssp, true);
-       else
-               retval = __srcu_read_lock(ssp);
+       srcu_check_nmi_safety(ssp, true);
+       retval = __srcu_read_lock_nmisafe(ssp);
        rcu_lock_acquire(&(ssp)->dep_map);
        return retval;
 }
@@ -205,6 +216,7 @@ srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp)
 {
        int retval;
 
+       srcu_check_nmi_safety(ssp, false);
        retval = __srcu_read_lock(ssp);
        return retval;
 }
@@ -220,6 +232,7 @@ static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx)
        __releases(ssp)
 {
        WARN_ON_ONCE(idx & ~0x1);
+       srcu_check_nmi_safety(ssp, false);
        rcu_lock_release(&(ssp)->dep_map);
        __srcu_read_unlock(ssp, idx);
 }
@@ -235,17 +248,16 @@ static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx)
        __releases(ssp)
 {
        WARN_ON_ONCE(idx & ~0x1);
+       srcu_check_nmi_safety(ssp, true);
        rcu_lock_release(&(ssp)->dep_map);
-       if (IS_ENABLED(CONFIG_NEED_SRCU_NMI_SAFE))
-               __srcu_read_unlock_nmisafe(ssp, idx, true);
-       else
-               __srcu_read_unlock(ssp, idx);
+       __srcu_read_unlock_nmisafe(ssp, idx);
 }
 
 /* Used by tracing, cannot be traced and cannot call lockdep. */
 static inline notrace void
 srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp)
 {
+       srcu_check_nmi_safety(ssp, false);
        __srcu_read_unlock(ssp, idx);
 }
 

diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
index 1ef8f2a4884f3139755c560dcb8f5519fe668f62..c689a81752c9aa354ebb2a50c56683a635fcdec0 100644 (file)
--- a/include/linux/srcutree.h
+++ b/include/linux/srcutree.h
@@ -43,10 +43,6 @@ struct srcu_data {
        struct srcu_struct *ssp;
 };
 
-#define SRCU_NMI_UNKNOWN       0x0
-#define SRCU_NMI_NMI_UNSAFE    0x1
-#define SRCU_NMI_NMI_SAFE      0x2
-
 /*
  * Node in SRCU combining tree, similar in function to rcu_data.
  */

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 272830a87e56659e4d7d32fe7def1e048e05bef8..ca4b5dcec675bacf421d24044f37c4a4042ef725 100644 (file)
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -631,17 +631,16 @@ void cleanup_srcu_struct(struct srcu_struct *ssp)
 }
 EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
 
+#ifdef CONFIG_PROVE_RCU
 /*
  * Check for consistent NMI safety.
  */
-static void srcu_check_nmi_safety(struct srcu_struct *ssp, bool nmi_safe)
+void srcu_check_nmi_safety(struct srcu_struct *ssp, bool nmi_safe)
 {
        int nmi_safe_mask = 1 << nmi_safe;
        int old_nmi_safe_mask;
        struct srcu_data *sdp;
 
-       if (!IS_ENABLED(CONFIG_PROVE_RCU))
-               return;
        /* NMI-unsafe use in NMI is a bad sign */
        WARN_ON_ONCE(!nmi_safe && in_nmi());
        sdp = raw_cpu_ptr(ssp->sda);
@@ -652,6 +651,8 @@ static void srcu_check_nmi_safety(struct srcu_struct *ssp, bool nmi_safe)
        }
        WARN_ONCE(old_nmi_safe_mask != nmi_safe_mask, "CPU %d old state %d new state %d\n", sdp->cpu, old_nmi_safe_mask, nmi_safe_mask);
 }
+EXPORT_SYMBOL_GPL(srcu_check_nmi_safety);
+#endif /* CONFIG_PROVE_RCU */
 
 /*
  * Counts the new reader in the appropriate per-CPU element of the
@@ -665,7 +666,6 @@ int __srcu_read_lock(struct srcu_struct *ssp)
        idx = READ_ONCE(ssp->srcu_idx) & 0x1;
        this_cpu_inc(ssp->sda->srcu_lock_count[idx].counter);
        smp_mb(); /* B */  /* Avoid leaking the critical section. */
-       srcu_check_nmi_safety(ssp, false);
        return idx;
 }
 EXPORT_SYMBOL_GPL(__srcu_read_lock);
@@ -679,7 +679,6 @@ void __srcu_read_unlock(struct srcu_struct *ssp, int idx)
 {
        smp_mb(); /* C */  /* Avoid leaking the critical section. */
        this_cpu_inc(ssp->sda->srcu_unlock_count[idx].counter);
-       srcu_check_nmi_safety(ssp, false);
 }
 EXPORT_SYMBOL_GPL(__srcu_read_unlock);
 
@@ -690,7 +689,7 @@ EXPORT_SYMBOL_GPL(__srcu_read_unlock);
  * srcu_struct, but in an NMI-safe manner using RMW atomics.
  * Returns an index that must be passed to the matching srcu_read_unlock().
  */
-int __srcu_read_lock_nmisafe(struct srcu_struct *ssp, bool chknmisafe)
+int __srcu_read_lock_nmisafe(struct srcu_struct *ssp)
 {
        int idx;
        struct srcu_data *sdp = raw_cpu_ptr(ssp->sda);
@@ -698,8 +697,6 @@ int __srcu_read_lock_nmisafe(struct srcu_struct *ssp, bool chknmisafe)
        idx = READ_ONCE(ssp->srcu_idx) & 0x1;
        atomic_long_inc(&sdp->srcu_lock_count[idx]);
        smp_mb__after_atomic(); /* B */  /* Avoid leaking the critical section. */
-       if (chknmisafe)
-               srcu_check_nmi_safety(ssp, true);
        return idx;
 }
 EXPORT_SYMBOL_GPL(__srcu_read_lock_nmisafe);
@@ -709,14 +706,12 @@ EXPORT_SYMBOL_GPL(__srcu_read_lock_nmisafe);
  * element of the srcu_struct.  Note that this may well be a different
  * CPU than that which was incremented by the corresponding srcu_read_lock().
  */
-void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx, bool chknmisafe)
+void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx)
 {
        struct srcu_data *sdp = raw_cpu_ptr(ssp->sda);
 
        smp_mb__before_atomic(); /* C */  /* Avoid leaking the critical section. */
        atomic_long_inc(&sdp->srcu_unlock_count[idx]);
-       if (chknmisafe)
-               srcu_check_nmi_safety(ssp, true);
 }
 EXPORT_SYMBOL_GPL(__srcu_read_unlock_nmisafe);
 
@@ -1163,7 +1158,7 @@ static unsigned long srcu_gp_start_if_needed(struct srcu_struct *ssp,
         * SRCU read-side critical section so that the grace-period
         * sequence number cannot wrap around in the meantime.
         */
-       idx = __srcu_read_lock_nmisafe(ssp, false);
+       idx = __srcu_read_lock_nmisafe(ssp);
        ss_state = smp_load_acquire(&ssp->srcu_size_state);
        if (ss_state < SRCU_SIZE_WAIT_CALL)
                sdp = per_cpu_ptr(ssp->sda, 0);
@@ -1196,7 +1191,7 @@ static unsigned long srcu_gp_start_if_needed(struct srcu_struct *ssp,
                srcu_funnel_gp_start(ssp, sdp, s, do_norm);
        else if (needexp)
                srcu_funnel_exp_start(ssp, sdp_mynode, s);
-       __srcu_read_unlock_nmisafe(ssp, idx, false);
+       __srcu_read_unlock_nmisafe(ssp, idx);
        return s;
 }
 
@@ -1500,13 +1495,13 @@ void srcu_barrier(struct srcu_struct *ssp)
        /* Initial count prevents reaching zero until all CBs are posted. */
        atomic_set(&ssp->srcu_barrier_cpu_cnt, 1);
 
-       idx = __srcu_read_lock_nmisafe(ssp, false);
+       idx = __srcu_read_lock_nmisafe(ssp);
        if (smp_load_acquire(&ssp->srcu_size_state) < SRCU_SIZE_WAIT_BARRIER)
                srcu_barrier_one_cpu(ssp, per_cpu_ptr(ssp->sda, 0));
        else
                for_each_possible_cpu(cpu)
                        srcu_barrier_one_cpu(ssp, per_cpu_ptr(ssp->sda, cpu));
-       __srcu_read_unlock_nmisafe(ssp, idx, false);
+       __srcu_read_unlock_nmisafe(ssp, idx);
 
        /* Remove the initial count, at which point reaching zero can happen. */
        if (atomic_dec_and_test(&ssp->srcu_barrier_cpu_cnt))