On Fri, Apr 02, 2021 at 01:47:03AM +0200, Frederic Weisbecker wrote:
> alloc_percpu() zeroes out the allocated memory. Therefore we can assume
> the whole struct srcu_data to be clear after calling it, just like after
> a static initialization. No need for a special treatment in the dynamic
> allocation case.
>
> Signed-off-by: Frederic Weisbecker
> Cc: Boqun Feng
> Cc: Lai Jiangshan
> Cc: Neeraj Upadhyay
> Cc: Josh Triplett
> Cc: Joel Fernandes
> Cc: Uladzislau Rezki
Good catch, thank you!!! I queued the following with the usual
wordsmithing, so as usual please let me know if I messed anything up.
Thanx, Paul
commit 2cfdfbfc41bcd96e7961a619e4a7f235b274f78f
Author: Frederic Weisbecker
Date: Fri Apr 2 01:47:03 2021 +0200
srcu: Remove superfluous sdp->srcu_lock_count zero filling
Because alloc_percpu() zeroes out the allocated memory, there is no need
to zero-fill newly allocated per-CPU memory. This commit therefore removes
the loop zeroing the ->srcu_lock_count and ->srcu_unlock_count arrays
from init_srcu_struct_nodes(). This is the only use of that function's
is_static parameter, which this commit also removes.
Signed-off-by: Frederic Weisbecker
Cc: Boqun Feng
Cc: Lai Jiangshan
Cc: Neeraj Upadhyay
Cc: Josh Triplett
Cc: Joel Fernandes
Cc: Uladzislau Rezki
Signed-off-by: Paul E. McKenney
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 036ff54..7389e46 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -80,7 +80,7 @@ do {
\
* srcu_read_unlock() running against them. So if the is_static parameter
* is set, don't initialize ->srcu_lock_count[] and ->srcu_unlock_count[].
*/
-static void init_srcu_struct_nodes(struct srcu_struct *ssp, bool is_static)
+static void init_srcu_struct_nodes(struct srcu_struct *ssp)
{
int cpu;
int i;
@@ -148,14 +148,6 @@ static void init_srcu_struct_nodes(struct srcu_struct
*ssp, bool is_static)
timer_setup(>delay_work, srcu_delay_timer, 0);
sdp->ssp = ssp;
sdp->grpmask = 1 << (cpu - sdp->mynode->grplo);
- if (is_static)
- continue;
-
- /* Dynamically allocated, better be no srcu_read_locks()! */
- for (i = 0; i < ARRAY_SIZE(sdp->srcu_lock_count); i++) {
- sdp->srcu_lock_count[i] = 0;
- sdp->srcu_unlock_count[i] = 0;
- }
}
}
@@ -179,7 +171,7 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp,
bool is_static)
ssp->sda = alloc_percpu(struct srcu_data);
if (!ssp->sda)
return -ENOMEM;
- init_srcu_struct_nodes(ssp, is_static);
+ init_srcu_struct_nodes(ssp);
ssp->srcu_gp_seq_needed_exp = 0;
ssp->srcu_last_gp_end = ktime_get_mono_fast_ns();
smp_store_release(>srcu_gp_seq_needed, 0); /* Init done. */
