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Message-Id: <20190716182642.GB22819@linux.ibm.com>
Date: Tue, 16 Jul 2019 11:26:42 -0700
From: "Paul E. McKenney" <paulmck@...ux.ibm.com>
To: "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc: linux-kernel@...r.kernel.org, Oleg Nesterov <oleg@...hat.com>,
Alexey Kuznetsov <kuznet@....inr.ac.ru>,
Bjorn Helgaas <bhelgaas@...gle.com>, Borislav Petkov <bp@...en8.de>,
c0d1n61at3@...il.com, "David S. Miller" <davem@...emloft.net>,
edumazet@...gle.com, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
Jonathan Corbet <corbet@....net>,
Josh Triplett <josh@...htriplett.org>, keescook@...omium.org,
kernel-hardening@...ts.openwall.com, kernel-team@...roid.com,
Lai Jiangshan <jiangshanlai@...il.com>, Len Brown <lenb@...nel.org>,
linux-acpi@...r.kernel.org, linux-doc@...r.kernel.org,
linux-pci@...r.kernel.org, linux-pm@...r.kernel.org,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, neilb@...e.com,
netdev@...r.kernel.org, Pavel Machek <pavel@....cz>,
peterz@...radead.org, "Rafael J. Wysocki" <rjw@...ysocki.net>,
Rasmus Villemoes <rasmus.villemoes@...vas.dk>, rcu@...r.kernel.org,
Steven Rostedt <rostedt@...dmis.org>, Tejun Heo <tj@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>, will@...nel.org,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>
Subject: Re: [PATCH v2 3/9] rcu/sync: Remove custom check for reader-section
On Fri, Jul 12, 2019 at 01:00:18PM -0400, Joel Fernandes (Google) wrote:
> The rcu/sync code was doing its own check whether we are in a reader
> section. With RCU consolidating flavors and the generic helper added in
> this series, this is no longer need. We can just use the generic helper
> and it results in a nice cleanup.
>
> Cc: Oleg Nesterov <oleg@...hat.com>
> Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
This needs to be forward-ported to current mainline. (Or, I believe
equivalently for this file, to branch "dev" of -rcu.)
Especially given that you have Oleg's Ack, I would be happy to
take the forward-ported version.
Thanx, Paul
> ---
> Please note: Only build and boot tested this particular patch so far.
>
> include/linux/rcu_sync.h | 5 ++---
> kernel/rcu/sync.c | 22 ----------------------
> 2 files changed, 2 insertions(+), 25 deletions(-)
>
> diff --git a/include/linux/rcu_sync.h b/include/linux/rcu_sync.h
> index 6fc53a1345b3..c954f1efc919 100644
> --- a/include/linux/rcu_sync.h
> +++ b/include/linux/rcu_sync.h
> @@ -39,9 +39,8 @@ extern void rcu_sync_lockdep_assert(struct rcu_sync *);
> */
> static inline bool rcu_sync_is_idle(struct rcu_sync *rsp)
> {
> -#ifdef CONFIG_PROVE_RCU
> - rcu_sync_lockdep_assert(rsp);
> -#endif
> + RCU_LOCKDEP_WARN(!rcu_read_lock_any_held(),
> + "suspicious rcu_sync_is_idle() usage");
> return !rsp->gp_state; /* GP_IDLE */
> }
>
> diff --git a/kernel/rcu/sync.c b/kernel/rcu/sync.c
> index a8304d90573f..535e02601f56 100644
> --- a/kernel/rcu/sync.c
> +++ b/kernel/rcu/sync.c
> @@ -10,37 +10,25 @@
> #include <linux/rcu_sync.h>
> #include <linux/sched.h>
>
> -#ifdef CONFIG_PROVE_RCU
> -#define __INIT_HELD(func) .held = func,
> -#else
> -#define __INIT_HELD(func)
> -#endif
> -
> static const struct {
> void (*sync)(void);
> void (*call)(struct rcu_head *, void (*)(struct rcu_head *));
> void (*wait)(void);
> -#ifdef CONFIG_PROVE_RCU
> - int (*held)(void);
> -#endif
> } gp_ops[] = {
> [RCU_SYNC] = {
> .sync = synchronize_rcu,
> .call = call_rcu,
> .wait = rcu_barrier,
> - __INIT_HELD(rcu_read_lock_held)
> },
> [RCU_SCHED_SYNC] = {
> .sync = synchronize_rcu,
> .call = call_rcu,
> .wait = rcu_barrier,
> - __INIT_HELD(rcu_read_lock_sched_held)
> },
> [RCU_BH_SYNC] = {
> .sync = synchronize_rcu,
> .call = call_rcu,
> .wait = rcu_barrier,
> - __INIT_HELD(rcu_read_lock_bh_held)
> },
> };
>
> @@ -49,16 +37,6 @@ enum { CB_IDLE = 0, CB_PENDING, CB_REPLAY };
>
> #define rss_lock gp_wait.lock
>
> -#ifdef CONFIG_PROVE_RCU
> -void rcu_sync_lockdep_assert(struct rcu_sync *rsp)
> -{
> - RCU_LOCKDEP_WARN(!gp_ops[rsp->gp_type].held(),
> - "suspicious rcu_sync_is_idle() usage");
> -}
> -
> -EXPORT_SYMBOL_GPL(rcu_sync_lockdep_assert);
> -#endif
> -
> /**
> * rcu_sync_init() - Initialize an rcu_sync structure
> * @rsp: Pointer to rcu_sync structure to be initialized
> --
> 2.22.0.510.g264f2c817a-goog
>
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