srcu: Make SRCU-fast also be NMI-safe

BPF uses rcu_read_lock_trace() in NMI context, so srcu_read_lock_fast()
must be NMI-safe if it is to have any chance of addressing RCU Tasks
Trace use cases. T

srcu: Make SRCU-fast also be NMI-safe

BPF uses rcu_read_lock_trace() in NMI context, so srcu_read_lock_fast()
must be NMI-safe if it is to have any chance of addressing RCU Tasks
Trace use cases. This commit therefore causes srcu_read_lock_fast()
and srcu_read_unlock_fast() to use atomic_long_inc() instead of
this_cpu_inc() on architectures that support NMIs but do not have
NMI-safe implementations of this_cpu_inc(). Note that both x86 and
arm64 have NMI-safe implementations of this_cpu_inc(), and thus do not
pay the performance penalty inherent in atomic_inc_long().

It is tempting to use this trick to fold srcu_read_lock_nmisafe()
into srcu_read_lock(), but this would need careful thought, review,
and performance analysis. Though those smp_mb() calls might well make
performance a non-issue.

Reported-by: Alexei Starovoitov <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>

show more ...

srcu: Add SRCU-fast readers

This commit adds srcu_read_{,un}lock_fast(), which is similar
to srcu_read_{,un}lock_lite(), but avoids the array-indexing and
pointer-following overhead. On a microbenc

srcu: Add SRCU-fast readers

This commit adds srcu_read_{,un}lock_fast(), which is similar
to srcu_read_{,un}lock_lite(), but avoids the array-indexing and
pointer-following overhead. On a microbenchmark featuring tight
loops around empty readers, this results in about a 20% speedup
compared to RCU Tasks Trace on my x86 laptop.

Please note that SRCU-fast has drawbacks compared to RCU Tasks
Trace, including:

o Lack of CPU stall warnings.
o SRCU-fast readers permitted only where rcu_is_watching().
o A pointer-sized return value from srcu_read_lock_fast() must
be passed to the corresponding srcu_read_unlock_fast().
o In the absence of readers, a synchronize_srcu() having _fast()
readers will incur the latency of at least two normal RCU grace
periods.
o RCU Tasks Trace priority boosting could be easily added.
Boosting SRCU readers is more difficult.

SRCU-fast also has a drawback compared to SRCU-lite, namely that the
return value from srcu_read_lock_fast()-fast is a 64-bit pointer and
that from srcu_read_lock_lite() is only a 32-bit int.

[ paulmck: Apply feedback from Akira Yokosawa. ]

Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>

show more ...

srcu: Move SRCU Tree/Tiny definitions from srcu.h

There are a couple of definitions under "#ifdef CONFIG_TINY_SRCU"
in include/linux/srcu.h. There is no point in them being there,
so this commit mo

srcu: Move SRCU Tree/Tiny definitions from srcu.h

There are a couple of definitions under "#ifdef CONFIG_TINY_SRCU"
in include/linux/srcu.h. There is no point in them being there,
so this commit moves them to include/linux/srcutiny.h and
include/linux/srcutree.c, thus eliminating that #ifdef.

Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>

show more ...

srcu: Pull integer-to-pointer conversion into __srcu_ctr_to_ptr()

This commit abstracts the srcu_read_unlock*() integer-to-pointer
conversion into a new __srcu_ctr_to_ptr(). This will be used
in rc

srcu: Pull integer-to-pointer conversion into __srcu_ctr_to_ptr()

This commit abstracts the srcu_read_unlock*() integer-to-pointer
conversion into a new __srcu_ctr_to_ptr(). This will be used
in rcutorture for testing an srcu_read_unlock_fast() that avoids
array-indexing overhead by taking a pointer rather than an integer.

[ paulmck: Apply kernel test robot feedback. ]

Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>

show more ...

srcu: Pull pointer-to-integer conversion into __srcu_ptr_to_ctr()

This commit abstracts the srcu_read_lock*() pointer-to-integer conversion
into a new __srcu_ptr_to_ctr(). This will be used in rcut

srcu: Pull pointer-to-integer conversion into __srcu_ptr_to_ctr()

This commit abstracts the srcu_read_lock*() pointer-to-integer conversion
into a new __srcu_ptr_to_ctr(). This will be used in rcutorture for
testing an srcu_read_lock_fast() that returns a pointer rather than
an integer.

Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>

show more ...

srcu: Rename srcu_check_read_flavor_lite() to srcu_check_read_flavor_force()

This commit renames the srcu_check_read_flavor_lite() function to
srcu_check_read_flavor_force() and adds a read_flavor a

srcu: Rename srcu_check_read_flavor_lite() to srcu_check_read_flavor_force()

This commit renames the srcu_check_read_flavor_lite() function to
srcu_check_read_flavor_force() and adds a read_flavor argument in order to
support an srcu_read_lock_fast() variant that is to avoid array indexing
in both the lock and unlock primitives.

Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>

show more ...

srcu: Make Tree SRCU updates independent of ->srcu_idx

This commit makes Tree SRCU updates independent of ->srcu_idx, then
drop ->srcu_idx.

Signed-off-by: Paul E. McKenney <[email protected]>
Cc:

srcu: Make Tree SRCU updates independent of ->srcu_idx

This commit makes Tree SRCU updates independent of ->srcu_idx, then
drop ->srcu_idx.

Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>

show more ...

srcu: Make SRCU readers use ->srcu_ctrs for counter selection

This commit causes SRCU readers to use ->srcu_ctrs for counter
selection instead of ->srcu_idx. This takes another step towards
array-i

srcu: Make SRCU readers use ->srcu_ctrs for counter selection

This commit causes SRCU readers to use ->srcu_ctrs for counter
selection instead of ->srcu_idx. This takes another step towards
array-indexing-free SRCU readers.

[ paulmck: Apply kernel test robot feedback. ]

Co-developed-by: Z qiang <[email protected]>
Signed-off-by: Z qiang <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Tested-by: kernel test robot <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>

show more ...

srcu: Pull ->srcu_{un,}lock_count into a new srcu_ctr structure

This commit prepares for array-index-free srcu_read_lock*() by moving the
->srcu_{un,}lock_count fields into a new srcu_ctr structure.

srcu: Pull ->srcu_{un,}lock_count into a new srcu_ctr structure

This commit prepares for array-index-free srcu_read_lock*() by moving the
->srcu_{un,}lock_count fields into a new srcu_ctr structure. This will
permit ->srcu_index to be replaced by a per-CPU pointer to this structure.

Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>

show more ...

srcu: Fix typo s/srcu_check_read_flavor()/__srcu_check_read_flavor()/

This commit fixes a typo in which a comment needed to have been updated
from srcu_check_read_flavor() to __srcu_check_read_flavo

srcu: Fix typo s/srcu_check_read_flavor()/__srcu_check_read_flavor()/

This commit fixes a typo in which a comment needed to have been updated
from srcu_check_read_flavor() to __srcu_check_read_flavor().

Reported-by: Neeraj Upadhyay <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
Signed-off-by: Paul E. McKenney <[email protected]>
Signed-off-by: Uladzislau Rezki (Sony) <[email protected]>

show more ...

rcutorture: Use symbols for SRCU reader flavors

This commit converts rcutorture.c values for the reader_flavor module
parameter from hexadecimal to the SRCU_READ_FLAVOR_* C-preprocessor
macros. The

rcutorture: Use symbols for SRCU reader flavors

This commit converts rcutorture.c values for the reader_flavor module
parameter from hexadecimal to the SRCU_READ_FLAVOR_* C-preprocessor
macros. The actual modprobe or kernel-boot-parameter values for
read_flavor must still be entered in hexadecimal.

Link: https://lore.kernel.org/all/[email protected]/

Suggested-by: Neeraj Upadhyay <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Signed-off-by: Uladzislau Rezki (Sony) <[email protected]>

show more ...

srcu: Unconditionally record srcu_read_lock_lite() in ->srcu_reader_flavor

Currently, srcu_read_lock_lite() uses the SRCU_READ_FLAVOR_LITE bit in
->srcu_reader_flavor to communicate to the grace-per

srcu: Unconditionally record srcu_read_lock_lite() in ->srcu_reader_flavor

Currently, srcu_read_lock_lite() uses the SRCU_READ_FLAVOR_LITE bit in
->srcu_reader_flavor to communicate to the grace-period processing in
srcu_readers_active_idx_check() that the smp_mb() must be replaced by a
synchronize_rcu(). Unfortunately, ->srcu_reader_flavor is not updated
unless the kernel is built with CONFIG_PROVE_RCU=y. Therefore in all
kernels built with CONFIG_PROVE_RCU=n, srcu_readers_active_idx_check()
incorrectly uses smp_mb() instead of synchronize_rcu() for srcu_struct
structures whose readers use srcu_read_lock_lite().

This commit therefore causes Tree SRCU srcu_read_lock_lite()
to unconditionally update ->srcu_reader_flavor so that
srcu_readers_active_idx_check() can make the correct choice.

Reported-by: Neeraj Upadhyay <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
Fixes: c0f08d6b5a61 ("srcu: Add srcu_read_lock_lite() and srcu_read_unlock_lite()")
Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Reviewed-by: Neeraj Upadhyay <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>

show more ...

srcu: Allow inlining of __srcu_read_{,un}lock_lite()

This commit moves __srcu_read_lock_lite() and __srcu_read_unlock_lite()
into include/linux/srcu.h and marks them "static inline" so that they
can

srcu: Allow inlining of __srcu_read_{,un}lock_lite()

This commit moves __srcu_read_lock_lite() and __srcu_read_unlock_lite()
into include/linux/srcu.h and marks them "static inline" so that they
can be inlined into srcu_read_lock_lite() and srcu_read_unlock_lite(),
respectively. They are not hand-inlined due to Tree SRCU and Tiny SRCU
having different implementations.

The earlier removal of smp_mb() combined with the inlining produce
significant single-percentage performance wins.

Link: https://lore.kernel.org/all/CAEf4BzYgiNmSb=ZKQ65tm6nJDi1UX2Gq26cdHSH1mPwXJYZj5g@mail.gmail.com/

Reported-by: Alexei Starovoitov <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: <[email protected]>
Reviewed-by: Neeraj Upadhyay <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>

show more ...

srcu: Add srcu_read_lock_lite() and srcu_read_unlock_lite()

This patch adds srcu_read_lock_lite() and srcu_read_unlock_lite(), which
dispense with the read-side smp_mb() but also are restricted to c

srcu: Add srcu_read_lock_lite() and srcu_read_unlock_lite()

This patch adds srcu_read_lock_lite() and srcu_read_unlock_lite(), which
dispense with the read-side smp_mb() but also are restricted to code
regions that RCU is watching. If a given srcu_struct structure uses
srcu_read_lock_lite() and srcu_read_unlock_lite(), it is not permitted
to use any other SRCU read-side marker, before, during, or after.

Another price of light-weight readers is heavier weight grace periods.
Such readers mean that SRCU grace periods on srcu_struct structures
used by light-weight readers will incur at least two calls to
synchronize_rcu(). In addition, normal SRCU grace periods for
light-weight-reader srcu_struct structures never auto-expedite.
Note that expedited SRCU grace periods for light-weight-reader
srcu_struct structures still invoke synchronize_rcu(), not
synchronize_srcu_expedited(). Something about wishing to keep
the IPIs down to a dull roar.

The srcu_read_lock_lite() and srcu_read_unlock_lite() functions may not
(repeat, *not*) be used from NMI handlers, but if this is needed, an
additional flavor of SRCU reader can be added by some future commit.

[ paulmck: Apply Alexei Starovoitov expediting feedback. ]
[ paulmck: Apply kernel test robot feedback. ]

Signed-off-by: Paul E. McKenney <[email protected]>
Tested-by: kernel test robot <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: <[email protected]>
Reviewed-by: Neeraj Upadhyay <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>

show more ...

srcu: Create CPP macros for normal and NMI-safe SRCU readers

This commit creates SRCU_READ_FLAVOR_NORMAL and SRCU_READ_FLAVOR_NMI
C-preprocessor macros for srcu_read_lock() and srcu_read_lock_nmisaf

srcu: Create CPP macros for normal and NMI-safe SRCU readers

This commit creates SRCU_READ_FLAVOR_NORMAL and SRCU_READ_FLAVOR_NMI
C-preprocessor macros for srcu_read_lock() and srcu_read_lock_nmisafe(),
respectively. These replace the old true/false values that were
previously passed to srcu_check_read_flavor(). In addition, the
srcu_check_read_flavor() function itself requires a bit of rework to
handle bitmasks instead of true/false values.

Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Reviewed-by: Neeraj Upadhyay <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>

show more ...

srcu: Renaming in preparation for additional reader flavor

Currently, there are only two flavors of readers, normal and NMI-safe.
A number of fields, functions, and types reflect this restriction.
T

srcu: Renaming in preparation for additional reader flavor

Currently, there are only two flavors of readers, normal and NMI-safe.
A number of fields, functions, and types reflect this restriction.
This renaming-only commit prepares for the addition of light-weight
(as in memory-barrier-free) readers. OK, OK, there is also a drive-by
white-space fixeup!

Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: <[email protected]>
Reviewed-by: Neeraj Upadhyay <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>

show more ...

srcu: faster gp seq wrap-around

Using a higher value for the initial gp sequence counters allows for
wrapping to occur faster. It can help with surfacing any issues that may
be happening as a result

srcu: faster gp seq wrap-around

Using a higher value for the initial gp sequence counters allows for
wrapping to occur faster. It can help with surfacing any issues that may
be happening as a result of the wrap around.

Signed-off-by: JP Kobryn <[email protected]>
Tested-by: Paul E. McKenney <[email protected]>
Signed-off-by: Neeraj Upadhyay <[email protected]>

show more ...

srcu: Add comments for srcu_size_state

The SRCU_SIZE_* names are not self-explanatory, so this commit therefore
adds comments to the definitions.

Signed-off-by: Pingfan Liu <[email protected]>
C

srcu: Add comments for srcu_size_state

The SRCU_SIZE_* names are not self-explanatory, so this commit therefore
adds comments to the definitions.

Signed-off-by: Pingfan Liu <[email protected]>
Cc: Lai Jiangshan <[email protected]>
Cc: "Paul E. McKenney" <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Josh Triplett <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: "Zhang, Qiang1" <[email protected]>
To: [email protected]
Reviewed-by: Paul E. McKenney <[email protected]>
Reviewed-by: Joel Fernandes (Google) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Signed-off-by: Joel Fernandes (Google) <[email protected]>

show more ...

srcu: Move work-scheduling fields from srcu_struct to srcu_usage

This commit moves the ->reschedule_jiffies, ->reschedule_count, and
->work fields from the srcu_struct structure to the srcu_usage st

srcu: Move work-scheduling fields from srcu_struct to srcu_usage

This commit moves the ->reschedule_jiffies, ->reschedule_count, and
->work fields from the srcu_struct structure to the srcu_usage structure
to reduce the size of the former in order to improve cache locality.

However, this means that the container_of() calls cannot get a pointer
to the srcu_struct because they are no longer in the srcu_struct.
This issue is addressed by adding a ->srcu_ssp field in the srcu_usage
structure that references the corresponding srcu_struct structure.
And given the presence of the sup pointer to the srcu_usage structure,
replace some ssp->srcu_usage-> instances with sup->.

[ paulmck Apply feedback from kernel test robot. ]

Link: https://lore.kernel.org/oe-kbuild-all/[email protected]/
Suggested-by: Christoph Hellwig <[email protected]>
Tested-by: Sachin Sant <[email protected]>
Tested-by: "Zhang, Qiang1" <[email protected]>
Tested-by: Joel Fernandes (Google) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

show more ...

srcu: Move srcu_barrier() fields from srcu_struct to srcu_usage

This commit moves the ->srcu_barrier_seq, ->srcu_barrier_mutex,
->srcu_barrier_completion, and ->srcu_barrier_cpu_cnt fields from the

srcu: Move srcu_barrier() fields from srcu_struct to srcu_usage

This commit moves the ->srcu_barrier_seq, ->srcu_barrier_mutex,
->srcu_barrier_completion, and ->srcu_barrier_cpu_cnt fields from the
srcu_struct structure to the srcu_usage structure to reduce the size of
the former in order to improve cache locality.

Suggested-by: Christoph Hellwig <[email protected]>
Tested-by: Sachin Sant <[email protected]>
Tested-by: "Zhang, Qiang1" <[email protected]>
Tested-by: Joel Fernandes (Google) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

show more ...

srcu: Move ->sda_is_static from srcu_struct to srcu_usage

This commit moves the ->sda_is_static field from the srcu_struct structure
to the srcu_usage structure to reduce the size of the former in o

srcu: Move ->sda_is_static from srcu_struct to srcu_usage

This commit moves the ->sda_is_static field from the srcu_struct structure
to the srcu_usage structure to reduce the size of the former in order
to improve cache locality.

Suggested-by: Christoph Hellwig <[email protected]>
Tested-by: Sachin Sant <[email protected]>
Tested-by: "Zhang, Qiang1" <[email protected]>
Tested-by: Joel Fernandes (Google) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

show more ...

srcu: Move heuristics fields from srcu_struct to srcu_usage

This commit moves the ->srcu_size_jiffies, ->srcu_n_lock_retries,
and ->srcu_n_exp_nodelay fields from the srcu_struct structure to the
sr

srcu: Move heuristics fields from srcu_struct to srcu_usage

This commit moves the ->srcu_size_jiffies, ->srcu_n_lock_retries,
and ->srcu_n_exp_nodelay fields from the srcu_struct structure to the
srcu_usage structure to reduce the size of the former in order to improve
cache locality.

Suggested-by: Christoph Hellwig <[email protected]>
Tested-by: Sachin Sant <[email protected]>
Tested-by: "Zhang, Qiang1" <[email protected]>
Tested-by: Joel Fernandes (Google) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

show more ...

srcu: Move grace-period fields from srcu_struct to srcu_usage

This commit moves the ->srcu_gp_seq, ->srcu_gp_seq_needed,
->srcu_gp_seq_needed_exp, ->srcu_gp_start, and ->srcu_last_gp_end fields
from

srcu: Move grace-period fields from srcu_struct to srcu_usage

This commit moves the ->srcu_gp_seq, ->srcu_gp_seq_needed,
->srcu_gp_seq_needed_exp, ->srcu_gp_start, and ->srcu_last_gp_end fields
from the srcu_struct structure to the srcu_usage structure to reduce
the size of the former in order to improve cache locality.

Suggested-by: Christoph Hellwig <[email protected]>
Tested-by: Sachin Sant <[email protected]>
Tested-by: "Zhang, Qiang1" <[email protected]>
Tested-by: Joel Fernandes (Google) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

show more ...

srcu: Move ->srcu_gp_mutex from srcu_struct to srcu_usage

This commit moves the ->srcu_gp_mutex field from the srcu_struct structure
to the srcu_usage structure to reduce the size of the former in o

srcu: Move ->srcu_gp_mutex from srcu_struct to srcu_usage

This commit moves the ->srcu_gp_mutex field from the srcu_struct structure
to the srcu_usage structure to reduce the size of the former in order
to improve cache locality.

Suggested-by: Christoph Hellwig <[email protected]>
Tested-by: Sachin Sant <[email protected]>
Tested-by: "Zhang, Qiang1" <[email protected]>
Tested-by: Joel Fernandes (Google) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

show more ...

srcu: Move ->lock from srcu_struct to srcu_usage

This commit moves the ->lock field from the srcu_struct structure to
the srcu_usage structure to reduce the size of the former in order to
improve ca

srcu: Move ->lock from srcu_struct to srcu_usage

This commit moves the ->lock field from the srcu_struct structure to
the srcu_usage structure to reduce the size of the former in order to
improve cache locality.

Suggested-by: Christoph Hellwig <[email protected]>
Tested-by: Sachin Sant <[email protected]>
Tested-by: "Zhang, Qiang1" <[email protected]>
Tested-by: Joel Fernandes (Google) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

show more ...