Messages in this thread Patch in this message | | | Date | Thu, 1 Apr 2021 17:58:21 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 2/3] srcu: Remove superfluous sdp->srcu_lock_count zero filling |
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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 <frederic@kernel.org> > Cc: Boqun Feng <boqun.feng@gmail.com> > Cc: Lai Jiangshan <jiangshanlai@gmail.com> > Cc: Neeraj Upadhyay <neeraju@codeaurora.org> > Cc: Josh Triplett <josh@joshtriplett.org> > Cc: Joel Fernandes <joel@joelfernandes.org> > Cc: Uladzislau Rezki <urezki@gmail.com>
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
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commit 2cfdfbfc41bcd96e7961a619e4a7f235b274f78f Author: Frederic Weisbecker <frederic@kernel.org> 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 <frederic@kernel.org> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Lai Jiangshan <jiangshanlai@gmail.com> Cc: Neeraj Upadhyay <neeraju@codeaurora.org> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Uladzislau Rezki <urezki@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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(&sdp->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(&ssp->srcu_gp_seq_needed, 0); /* Init done. */
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