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 V2 19/20] bpf, lpm: Make locking RT friendly
Date: Thu, 20 Feb 2020 21:45:36 +0100 [thread overview]
Message-ID: <20200220204619.234597434@linutronix.de> (raw)
In-Reply-To: 20200220204517.863202864@linutronix.de
The LPM trie map cannot be used in contexts like perf, kprobes and tracing
as this map type dynamically allocates memory.
The memory allocation happens with a raw spinlock held which is a truly
spinning lock on a PREEMPT RT enabled kernel which disables preemption and
interrupts.
As RT does not allow memory allocation from such a section for various
reasons, convert the raw spinlock to a regular spinlock.
On a RT enabled kernel these locks are substituted by 'sleeping' spinlocks
which provide the proper protection but keep the code preemptible.
On a non-RT kernel regular spinlocks map to raw spinlocks, i.e. this does
not cause any functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/bpf/lpm_trie.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
--- a/kernel/bpf/lpm_trie.c
+++ b/kernel/bpf/lpm_trie.c
@@ -34,7 +34,7 @@ struct lpm_trie {
size_t n_entries;
size_t max_prefixlen;
size_t data_size;
- raw_spinlock_t lock;
+ spinlock_t lock;
};
/* This trie implements a longest prefix match algorithm that can be used to
@@ -315,7 +315,7 @@ static int trie_update_elem(struct bpf_m
if (key->prefixlen > trie->max_prefixlen)
return -EINVAL;
- raw_spin_lock_irqsave(&trie->lock, irq_flags);
+ spin_lock_irqsave(&trie->lock, irq_flags);
/* Allocate and fill a new node */
@@ -422,7 +422,7 @@ static int trie_update_elem(struct bpf_m
kfree(im_node);
}
- raw_spin_unlock_irqrestore(&trie->lock, irq_flags);
+ spin_unlock_irqrestore(&trie->lock, irq_flags);
return ret;
}
@@ -442,7 +442,7 @@ static int trie_delete_elem(struct bpf_m
if (key->prefixlen > trie->max_prefixlen)
return -EINVAL;
- raw_spin_lock_irqsave(&trie->lock, irq_flags);
+ spin_lock_irqsave(&trie->lock, irq_flags);
/* Walk the tree looking for an exact key/length match and keeping
* track of the path we traverse. We will need to know the node
@@ -518,7 +518,7 @@ static int trie_delete_elem(struct bpf_m
kfree_rcu(node, rcu);
out:
- raw_spin_unlock_irqrestore(&trie->lock, irq_flags);
+ spin_unlock_irqrestore(&trie->lock, irq_flags);
return ret;
}
@@ -575,7 +575,7 @@ static struct bpf_map *trie_alloc(union
if (ret)
goto out_err;
- raw_spin_lock_init(&trie->lock);
+ spin_lock_init(&trie->lock);
return &trie->map;
out_err:
next prev parent reply other threads:[~2020-02-20 20:58 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-20 20:45 [patch V2 00/20] bpf: Make BPF and PREEMPT_RT co-exist Thomas Gleixner
2020-02-20 20:45 ` [patch V2 01/20] bpf: Enforce preallocation for all instrumentation programs Thomas Gleixner
2020-02-22 4:29 ` Alexei Starovoitov
2020-02-22 8:40 ` Thomas Gleixner
2020-02-23 22:40 ` Alexei Starovoitov
2020-02-22 16:44 ` kbuild test robot
2020-02-20 20:45 ` [patch V2 02/20] bpf: Update locking comment in hashtab code Thomas Gleixner
2020-02-20 20:45 ` [patch V2 03/20] bpf/tracing: Remove redundant preempt_disable() in __bpf_trace_run() Thomas Gleixner
2020-02-20 20:45 ` [patch V2 04/20] perf/bpf: Remove preempt disable around BPF invocation Thomas Gleixner
2020-02-20 20:45 ` [patch V2 05/20] bpf: Remove recursion prevention from rcu free callback Thomas Gleixner
2020-02-20 20:45 ` [patch V2 06/20] bpf: Dont iterate over possible CPUs with interrupts disabled Thomas Gleixner
2020-02-20 20:45 ` [patch V2 07/20] bpf: Provide bpf_prog_run_pin_on_cpu() helper Thomas Gleixner
2020-02-20 20:45 ` [patch V2 08/20] bpf: Replace cant_sleep() with cant_migrate() Thomas Gleixner
2020-02-20 20:45 ` [patch V2 09/20] bpf: Use bpf_prog_run_pin_on_cpu() at simple call sites Thomas Gleixner
2020-02-20 20:45 ` [patch V2 10/20] trace/bpf: Use migrate disable in trace_call_bpf() Thomas Gleixner
2020-02-20 20:45 ` [patch V2 11/20] bpf/tests: Use migrate disable instead of preempt disable Thomas Gleixner
2020-02-20 20:45 ` [patch V2 12/20] bpf: Use migrate_disable/enabe() in trampoline code Thomas Gleixner
2020-02-20 20:45 ` [patch V2 13/20] bpf: Use migrate_disable/enable in array macros and cgroup/lirc code Thomas Gleixner
2020-02-20 20:45 ` [patch V2 14/20] bpf: Use migrate_disable() in hashtab code Thomas Gleixner
2020-02-20 20:45 ` [patch V2 15/20] bpf: Provide recursion prevention helpers Thomas Gleixner
2020-02-20 20:45 ` [patch V2 16/20] bpf: Replace open coded recursion prevention Thomas Gleixner
2020-02-20 20:45 ` [patch V2 17/20] bpf: Factor out hashtab bucket lock operations Thomas Gleixner
2020-02-20 20:45 ` [patch V2 18/20] bpf: Prepare hashtab locking for PREEMPT_RT Thomas Gleixner
2020-02-20 20:45 ` Thomas Gleixner [this message]
2020-02-20 20:45 ` [patch V2 20/20] bpf/stackmap: Dont trylock mmap_sem with PREEMPT_RT and interrupts disabled Thomas Gleixner
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