On Mon, Oct 14, 2024 at 09:49:52AM -0700, Paul E. McKenney wrote: > On Mon, Oct 14, 2024 at 02:45:50PM +0530, Neeraj Upadhyay wrote: > > On 10/9/2024 11:37 PM, Paul E. McKenney wrote: > > > This commit changes a few "cpuc" variables to "sdp" to align wiht usage > > > elsewhere. > > > > > > > s/wiht/with/ > > Good eyes! And fixed. > > This commit is doing a lot more than renaming "cpuc". > > Indeed, it does look like I forgot to commit between two changes. > > It looks like this commit log goes with the changes to the > functions srcu_readers_lock_idx(), srcu_readers_unlock_idx(), and > srcu_readers_active(). With the exception of the change from "NMI-safe" > to "reader flavors in the WARN_ONCE() string in srcu_readers_unlock_idx(). > > How would you suggest that I split up the non-s/cpuc/sdp/ changes? As a first step, I split it three ways, as you can see on the updated "dev" branch in the -rcu tree. Thoughts? Thanx, Paul > > - Neeraj > > > > > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx> > > > Cc: Alexei Starovoitov <ast@xxxxxxxxxx> > > > Cc: Andrii Nakryiko <andrii@xxxxxxxxxx> > > > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > > > Cc: Kent Overstreet <kent.overstreet@xxxxxxxxx> > > > Cc: <bpf@xxxxxxxxxxxxxxx> > > > --- > > > include/linux/srcu.h | 35 ++++++++++++++++++---------------- > > > include/linux/srcutree.h | 4 ++++ > > > kernel/rcu/srcutree.c | 41 ++++++++++++++++++++-------------------- > > > 3 files changed, 44 insertions(+), 36 deletions(-) > > > > > > diff --git a/include/linux/srcu.h b/include/linux/srcu.h > > > index 06728ef6f32a4..84daaa33ea0ab 100644 > > > --- a/include/linux/srcu.h > > > +++ b/include/linux/srcu.h > > > @@ -176,10 +176,6 @@ 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_read_flavor(struct srcu_struct *ssp, int read_flavor); > > > #else > > > @@ -235,16 +231,19 @@ static inline void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flav > > > * a mutex that is held elsewhere while calling synchronize_srcu() or > > > * synchronize_srcu_expedited(). > > > * > > > - * Note that srcu_read_lock() and the matching srcu_read_unlock() must > > > - * occur in the same context, for example, it is illegal to invoke > > > - * srcu_read_unlock() in an irq handler if the matching srcu_read_lock() > > > - * was invoked in process context. > > > + * The return value from srcu_read_lock() must be passed unaltered > > > + * to the matching srcu_read_unlock(). Note that srcu_read_lock() and > > > + * the matching srcu_read_unlock() must occur in the same context, for > > > + * example, it is illegal to invoke srcu_read_unlock() in an irq handler > > > + * if the matching srcu_read_lock() was invoked in process context. Or, > > > + * for that matter to invoke srcu_read_unlock() from one task and the > > > + * matching srcu_read_lock() from another. > > > */ > > > static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp) > > > { > > > int retval; > > > > > > - srcu_check_read_flavor(ssp, false); > > > + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); > > > retval = __srcu_read_lock(ssp); > > > srcu_lock_acquire(&ssp->dep_map); > > > return retval; > > > @@ -256,12 +255,16 @@ static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp) > > > * > > > * Enter an SRCU read-side critical section, but in an NMI-safe manner. > > > * See srcu_read_lock() for more information. > > > + * > > > + * If srcu_read_lock_nmisafe() is ever used on an srcu_struct structure, > > > + * then none of the other flavors may be used, whether before, during, > > > + * or after. > > > */ > > > static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp) > > > { > > > int retval; > > > > > > - srcu_check_read_flavor(ssp, true); > > > + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NMI); > > > retval = __srcu_read_lock_nmisafe(ssp); > > > rcu_try_lock_acquire(&ssp->dep_map); > > > return retval; > > > @@ -273,7 +276,7 @@ srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp) > > > { > > > int retval; > > > > > > - srcu_check_read_flavor(ssp, false); > > > + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); > > > retval = __srcu_read_lock(ssp); > > > return retval; > > > } > > > @@ -302,7 +305,7 @@ srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp) > > > static inline int srcu_down_read(struct srcu_struct *ssp) __acquires(ssp) > > > { > > > WARN_ON_ONCE(in_nmi()); > > > - srcu_check_read_flavor(ssp, false); > > > + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); > > > return __srcu_read_lock(ssp); > > > } > > > > > > @@ -317,7 +320,7 @@ static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx) > > > __releases(ssp) > > > { > > > WARN_ON_ONCE(idx & ~0x1); > > > - srcu_check_read_flavor(ssp, false); > > > + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); > > > srcu_lock_release(&ssp->dep_map); > > > __srcu_read_unlock(ssp, idx); > > > } > > > @@ -333,7 +336,7 @@ static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) > > > __releases(ssp) > > > { > > > WARN_ON_ONCE(idx & ~0x1); > > > - srcu_check_read_flavor(ssp, true); > > > + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NMI); > > > rcu_lock_release(&ssp->dep_map); > > > __srcu_read_unlock_nmisafe(ssp, idx); > > > } > > > @@ -342,7 +345,7 @@ static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) > > > static inline notrace void > > > srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp) > > > { > > > - srcu_check_read_flavor(ssp, false); > > > + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); > > > __srcu_read_unlock(ssp, idx); > > > } > > > > > > @@ -359,7 +362,7 @@ static inline void srcu_up_read(struct srcu_struct *ssp, int idx) > > > { > > > WARN_ON_ONCE(idx & ~0x1); > > > WARN_ON_ONCE(in_nmi()); > > > - srcu_check_read_flavor(ssp, false); > > > + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); > > > __srcu_read_unlock(ssp, idx); > > > } > > > > > > diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h > > > index ab7d8d215b84b..79ad809c7f035 100644 > > > --- a/include/linux/srcutree.h > > > +++ b/include/linux/srcutree.h > > > @@ -43,6 +43,10 @@ struct srcu_data { > > > struct srcu_struct *ssp; > > > }; > > > > > > +/* Values for ->srcu_reader_flavor. */ > > > +#define SRCU_READ_FLAVOR_NORMAL 0x1 // srcu_read_lock(). > > > +#define SRCU_READ_FLAVOR_NMI 0x2 // srcu_read_lock_nmisafe(). > > > + > > > /* > > > * Node in SRCU combining tree, similar in function to rcu_data. > > > */ > > > diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c > > > index abe55777c4335..4c51be484b48a 100644 > > > --- a/kernel/rcu/srcutree.c > > > +++ b/kernel/rcu/srcutree.c > > > @@ -438,9 +438,9 @@ static unsigned long srcu_readers_lock_idx(struct srcu_struct *ssp, int idx) > > > unsigned long sum = 0; > > > > > > for_each_possible_cpu(cpu) { > > > - struct srcu_data *cpuc = per_cpu_ptr(ssp->sda, cpu); > > > + struct srcu_data *sdp = per_cpu_ptr(ssp->sda, cpu); > > > > > > - sum += atomic_long_read(&cpuc->srcu_lock_count[idx]); > > > + sum += atomic_long_read(&sdp->srcu_lock_count[idx]); > > > } > > > return sum; > > > } > > > @@ -456,14 +456,14 @@ static unsigned long srcu_readers_unlock_idx(struct srcu_struct *ssp, int idx) > > > unsigned long sum = 0; > > > > > > for_each_possible_cpu(cpu) { > > > - struct srcu_data *cpuc = per_cpu_ptr(ssp->sda, cpu); > > > + struct srcu_data *sdp = per_cpu_ptr(ssp->sda, cpu); > > > > > > - sum += atomic_long_read(&cpuc->srcu_unlock_count[idx]); > > > + sum += atomic_long_read(&sdp->srcu_unlock_count[idx]); > > > if (IS_ENABLED(CONFIG_PROVE_RCU)) > > > - mask = mask | READ_ONCE(cpuc->srcu_reader_flavor); > > > + mask = mask | READ_ONCE(sdp->srcu_reader_flavor); > > > } > > > WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && (mask & (mask - 1)), > > > - "Mixed NMI-safe readers for srcu_struct at %ps.\n", ssp); > > > + "Mixed reader flavors for srcu_struct at %ps.\n", ssp); > > > return sum; > > > } > > > > > > @@ -564,12 +564,12 @@ static bool srcu_readers_active(struct srcu_struct *ssp) > > > unsigned long sum = 0; > > > > > > for_each_possible_cpu(cpu) { > > > - struct srcu_data *cpuc = per_cpu_ptr(ssp->sda, cpu); > > > + struct srcu_data *sdp = per_cpu_ptr(ssp->sda, cpu); > > > > > > - sum += atomic_long_read(&cpuc->srcu_lock_count[0]); > > > - sum += atomic_long_read(&cpuc->srcu_lock_count[1]); > > > - sum -= atomic_long_read(&cpuc->srcu_unlock_count[0]); > > > - sum -= atomic_long_read(&cpuc->srcu_unlock_count[1]); > > > + sum += atomic_long_read(&sdp->srcu_lock_count[0]); > > > + sum += atomic_long_read(&sdp->srcu_lock_count[1]); > > > + sum -= atomic_long_read(&sdp->srcu_unlock_count[0]); > > > + sum -= atomic_long_read(&sdp->srcu_unlock_count[1]); > > > } > > > return sum; > > > } > > > @@ -703,20 +703,21 @@ EXPORT_SYMBOL_GPL(cleanup_srcu_struct); > > > */ > > > void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor) > > > { > > > - int reader_flavor_mask = 1 << read_flavor; > > > - int old_reader_flavor_mask; > > > + int old_read_flavor; > > > struct srcu_data *sdp; > > > > > > - /* NMI-unsafe use in NMI is a bad sign */ > > > - WARN_ON_ONCE(!read_flavor && in_nmi()); > > > + /* NMI-unsafe use in NMI is a bad sign, as is multi-bit read_flavor values. */ > > > + WARN_ON_ONCE((read_flavor != SRCU_READ_FLAVOR_NMI) && in_nmi()); > > > + WARN_ON_ONCE(read_flavor & (read_flavor - 1)); > > > + > > > sdp = raw_cpu_ptr(ssp->sda); > > > - old_reader_flavor_mask = READ_ONCE(sdp->srcu_reader_flavor); > > > - if (!old_reader_flavor_mask) { > > > - old_reader_flavor_mask = cmpxchg(&sdp->srcu_reader_flavor, 0, reader_flavor_mask); > > > - if (!old_reader_flavor_mask) > > > + old_read_flavor = READ_ONCE(sdp->srcu_reader_flavor); > > > + if (!old_read_flavor) { > > > + old_read_flavor = cmpxchg(&sdp->srcu_reader_flavor, 0, read_flavor); > > > + if (!old_read_flavor) > > > return; > > > } > > > - WARN_ONCE(old_reader_flavor_mask != reader_flavor_mask, "CPU %d old state %d new state %d\n", sdp->cpu, old_reader_flavor_mask, reader_flavor_mask); > > > + WARN_ONCE(old_read_flavor != read_flavor, "CPU %d old state %d new state %d\n", sdp->cpu, old_read_flavor, read_flavor); > > > } > > > EXPORT_SYMBOL_GPL(srcu_check_read_flavor); > > > #endif /* CONFIG_PROVE_RCU */ > >