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

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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>
This commit is contained in:
Frederic Weisbecker 2022-10-13 19:22:44 +02:00 committed by Paul E. McKenney
parent ae3c070616
commit e29a4915db
3 changed files with 34 additions and 31 deletions
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36
include/linux/srcu.h
View file

@ -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);
}

4
include/linux/srcutree.h
View file

@ -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.
*/

25
kernel/rcu/srcutree.c
View file

@ -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))