From: Thomas Gleixner <tglx@linutronix•de>
To: LKML <linux-kernel@vger•kernel.org>
Cc: David Miller <davem@davemloft•net>,
bpf@vger•kernel.org, netdev@vger•kernel.org,
Alexei Starovoitov <ast@kernel•org>,
Daniel Borkmann <daniel@iogearbox•net>,
Sebastian Sewior <bigeasy@linutronix•de>,
Peter Zijlstra <peterz@infradead•org>,
Clark Williams <williams@redhat•com>,
Steven Rostedt <rostedt@goodmis•org>,
Juri Lelli <juri.lelli@redhat•com>,
Ingo Molnar <mingo@kernel•org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios•com>,
Vinicius Costa Gomes <vinicius.gomes@intel•com>,
Jakub Kicinski <kuba@kernel•org>
Subject: [patch V3 09/22] bpf: Dont iterate over possible CPUs with interrupts disabled
Date: Mon, 24 Feb 2020 15:01:40 +0100 [thread overview]
Message-ID: <20200224145643.365930116@linutronix.de> (raw)
In-Reply-To: 20200224140131.461979697@linutronix.de
pcpu_freelist_populate() is disabling interrupts and then iterates over the
possible CPUs. The reason why this disables interrupts is to silence
lockdep because the invoked ___pcpu_freelist_push() takes spin locks.
Neither the interrupt disabling nor the locking are required in this
function because it's called during initialization and the resulting map is
not yet visible to anything.
Split out the actual push assignement into an inline, call it from the loop
and remove the interrupt disable.
Signed-off-by: Thomas Gleixner <tglx@linutronix•de>
---
kernel/bpf/percpu_freelist.c | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)
--- a/kernel/bpf/percpu_freelist.c
+++ b/kernel/bpf/percpu_freelist.c
@@ -25,12 +25,18 @@ void pcpu_freelist_destroy(struct pcpu_f
free_percpu(s->freelist);
}
+static inline void pcpu_freelist_push_node(struct pcpu_freelist_head *head,
+ struct pcpu_freelist_node *node)
+{
+ node->next = head->first;
+ head->first = node;
+}
+
static inline void ___pcpu_freelist_push(struct pcpu_freelist_head *head,
struct pcpu_freelist_node *node)
{
raw_spin_lock(&head->lock);
- node->next = head->first;
- head->first = node;
+ pcpu_freelist_push_node(head, node);
raw_spin_unlock(&head->lock);
}
@@ -56,21 +62,16 @@ void pcpu_freelist_populate(struct pcpu_
u32 nr_elems)
{
struct pcpu_freelist_head *head;
- unsigned long flags;
int i, cpu, pcpu_entries;
pcpu_entries = nr_elems / num_possible_cpus() + 1;
i = 0;
- /* disable irq to workaround lockdep false positive
- * in bpf usage pcpu_freelist_populate() will never race
- * with pcpu_freelist_push()
- */
- local_irq_save(flags);
for_each_possible_cpu(cpu) {
again:
head = per_cpu_ptr(s->freelist, cpu);
- ___pcpu_freelist_push(head, buf);
+ /* No locking required as this is not visible yet. */
+ pcpu_freelist_push_node(head, buf);
i++;
buf += elem_size;
if (i == nr_elems)
@@ -78,7 +79,6 @@ void pcpu_freelist_populate(struct pcpu_
if (i % pcpu_entries)
goto again;
}
- local_irq_restore(flags);
}
struct pcpu_freelist_node *__pcpu_freelist_pop(struct pcpu_freelist *s)
next prev parent reply other threads:[~2020-02-24 15:04 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-24 14:01 [patch V3 00/22] bpf: Make BPF and PREEMPT_RT co-exist Thomas Gleixner
2020-02-24 14:01 ` [patch V3 01/22] bpf: Tighten the requirements for preallocated hash maps Thomas Gleixner
2020-02-24 14:01 ` [patch V3 02/22] bpf: Enforce preallocation for instrumentation programs on RT Thomas Gleixner
2020-02-24 14:01 ` [patch V3 03/22] bpf: Update locking comment in hashtab code Thomas Gleixner
2020-02-24 14:01 ` [patch V3 04/22] bpf/tracing: Remove redundant preempt_disable() in __bpf_trace_run() Thomas Gleixner
2020-02-24 14:01 ` [patch V3 05/22] bpf/trace: Remove EXPORT from trace_call_bpf() Thomas Gleixner
2020-02-24 18:16 ` Alexei Starovoitov
2020-02-24 14:01 ` [patch V3 06/22] bpf/trace: Remove redundant preempt_disable " Thomas Gleixner
2020-02-24 19:40 ` Alexei Starovoitov
2020-02-24 20:42 ` Thomas Gleixner
2020-02-25 0:33 ` Alexei Starovoitov
2020-02-25 12:36 ` Thomas Gleixner
2020-02-24 14:01 ` [patch V3 07/22] perf/bpf: Remove preempt disable around BPF invocation Thomas Gleixner
2020-02-24 14:01 ` [patch V3 08/22] bpf: Remove recursion prevention from rcu free callback Thomas Gleixner
2020-02-24 14:01 ` Thomas Gleixner [this message]
2020-02-24 14:01 ` [patch V3 10/22] bpf: Provide bpf_prog_run_pin_on_cpu() helper Thomas Gleixner
2020-02-24 18:14 ` Thomas Gleixner
2020-02-24 18:41 ` [patch V4 " Thomas Gleixner
2020-02-24 14:01 ` [patch V3 11/22] bpf: Replace cant_sleep() with cant_migrate() Thomas Gleixner
2020-02-24 14:01 ` [patch V3 12/22] bpf: Use bpf_prog_run_pin_on_cpu() at simple call sites Thomas Gleixner
2020-02-24 14:01 ` [patch V3 13/22] bpf/tests: Use migrate disable instead of preempt disable Thomas Gleixner
2020-02-24 14:01 ` [patch V3 14/22] bpf: Use migrate_disable/enabe() in trampoline code Thomas Gleixner
2020-02-24 14:01 ` [patch V3 15/22] bpf: Use migrate_disable/enable in array macros and cgroup/lirc code Thomas Gleixner
2020-02-24 14:01 ` [patch V3 16/22] bpf: Provide recursion prevention helpers Thomas Gleixner
2020-02-24 14:01 ` [patch V3 17/22] bpf: Use recursion prevention helpers in hashtab code Thomas Gleixner
2020-02-24 14:01 ` [patch V3 18/22] bpf: Replace open coded recursion prevention in sys_bpf() Thomas Gleixner
2020-02-24 14:01 ` [patch V3 19/22] bpf: Factor out hashtab bucket lock operations Thomas Gleixner
2020-02-24 14:01 ` [patch V3 20/22] bpf: Prepare hashtab locking for PREEMPT_RT Thomas Gleixner
2020-02-24 14:01 ` [patch V3 21/22] bpf, lpm: Make locking RT friendly Thomas Gleixner
2020-02-24 14:01 ` [patch V3 22/22] bpf/stackmap: Dont trylock mmap_sem with PREEMPT_RT and interrupts disabled Thomas Gleixner
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