diff options
| author | Paul E. McKenney <paulmck@kernel.org> | 2024-10-15 09:11:05 -0700 |
|---|---|---|
| committer | Frederic Weisbecker <frederic@kernel.org> | 2024-11-12 15:43:34 +0100 |
| commit | 6364dd8191d27230176ac4b1b4daaecaf4807399 (patch) | |
| tree | 10363ede4113fbab92f20c8c9c7d2f1122ae26ca /include/linux/srcutree.h | |
| parent | 05829be27fe6f64e0675dc3be3a12d43b52492e1 (diff) | |
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 <paulmck@kernel.org>
Tested-by: kernel test robot <oliver.sang@intel.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: <bpf@vger.kernel.org>
Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Diffstat (limited to 'include/linux/srcutree.h')
| -rw-r--r-- | include/linux/srcutree.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index 79ad809c7f03..8074138cbd62 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -46,6 +46,7 @@ struct srcu_data { /* Values for ->srcu_reader_flavor. */ #define SRCU_READ_FLAVOR_NORMAL 0x1 // srcu_read_lock(). #define SRCU_READ_FLAVOR_NMI 0x2 // srcu_read_lock_nmisafe(). +#define SRCU_READ_FLAVOR_LITE 0x4 // srcu_read_lock_lite(). /* * Node in SRCU combining tree, similar in function to rcu_data. |