From: Peter Zijlstra <peterz@infradead.org>
To: Amol Grover <frextrite@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
linux-kernel@vger.kernel.org,
linux-kernel-mentees@lists.linuxfoundation.org,
Joel Fernandes <joel@joelfernandes.org>,
Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com>,
"Paul E . McKenney" <paulmck@kernel.org>
Subject: Re: [PATCH RESEND] lockdep: Pass lockdep expression to RCU lists
Date: Mon, 17 Feb 2020 16:12:46 +0100 [thread overview]
Message-ID: <20200217151246.GS14897@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200216074636.GB14025@workstation-portable>
On Sun, Feb 16, 2020 at 01:16:36PM +0530, Amol Grover wrote:
> Data is traversed using hlist_for_each_entry_rcu outside an
> RCU read-side critical section but under the protection
> of either lockdep_lock or with irqs disabled.
>
> Hence, add corresponding lockdep expression to silence false-positive
> lockdep warnings, and harden RCU lists. Also add macro for
> corresponding lockdep expression.
>
> Two things to note:
> - RCU traversals protected under both, irqs disabled and
> graph lock, have both the checks in the lockdep expression.
> - RCU traversals under the protection of just disabled irqs
> don't have a corresponding lockdep expression as it is implicitly
> checked for.
>
> Signed-off-by: Amol Grover <frextrite@gmail.com>
> ---
> kernel/locking/lockdep.c | 21 +++++++++++++--------
> 1 file changed, 13 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index 32282e7112d3..696ad5d4daed 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -85,6 +85,8 @@ module_param(lock_stat, int, 0644);
> * code to recurse back into the lockdep code...
> */
> static arch_spinlock_t lockdep_lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
> +#define graph_lock_held() \
> + arch_spin_is_locked(&lockdep_lock)
> static struct task_struct *lockdep_selftest_task_struct;
>
> static int graph_lock(void)
> @@ -1009,7 +1011,7 @@ static bool __check_data_structures(void)
> /* Check the chain_key of all lock chains. */
> for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
> head = chainhash_table + i;
> - hlist_for_each_entry_rcu(chain, head, entry) {
> + hlist_for_each_entry_rcu(chain, head, entry, graph_lock_held()) {
> if (!check_lock_chain_key(chain))
> return false;
> }
URGH.. this patch combines two horribles to create a horrific :/
- spin_is_locked() is an abomination
- this RCU list stuff is just plain annoying
I'm tempted to do something like:
#define STFU (true)
hlist_for_each_entry_rcu(chain, head, entry, STFU) {
Paul, are we going a little over-board with this stuff? Do we really
have to annotate all of this?
next prev parent reply other threads:[~2020-02-17 15:12 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-16 7:46 [PATCH RESEND] lockdep: Pass lockdep expression to RCU lists Amol Grover
2020-02-17 15:12 ` Peter Zijlstra [this message]
2020-02-17 16:35 ` Joel Fernandes
2020-02-17 18:28 ` Paul E. McKenney
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