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 17/22] bpf: Use recursion prevention helpers in hashtab code
Date: Mon, 24 Feb 2020 15:01:48 +0100 [thread overview]
Message-ID: <20200224145644.211208533@linutronix.de> (raw)
In-Reply-To: 20200224140131.461979697@linutronix.de
The required protection is that the caller cannot be migrated to a
different CPU as these places take either a hash bucket lock or might
trigger a kprobe inside the memory allocator. Both scenarios can lead to
deadlocks. The deadlock prevention is per CPU by incrementing a per CPU
variable which temporarily blocks the invocation of BPF programs from perf
and kprobes.
Replace the open coded preempt_disable/enable() and this_cpu_inc/dec()
pairs with the new recursion prevention helpers to prepare BPF to work on
PREEMPT_RT enabled kernels. On a non-RT kernel the migrate disable/enable
in the helpers map to preempt_disable/enable(), i.e. no functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
V3: Use recursion prevention helpers consistently
---
kernel/bpf/hashtab.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -1333,8 +1333,7 @@ static int
}
again:
- preempt_disable();
- this_cpu_inc(bpf_prog_active);
+ bpf_disable_instrumentation();
rcu_read_lock();
again_nocopy:
dst_key = keys;
@@ -1362,8 +1361,7 @@ static int
*/
raw_spin_unlock_irqrestore(&b->lock, flags);
rcu_read_unlock();
- this_cpu_dec(bpf_prog_active);
- preempt_enable();
+ bpf_enable_instrumentation();
goto after_loop;
}
@@ -1374,8 +1372,7 @@ static int
*/
raw_spin_unlock_irqrestore(&b->lock, flags);
rcu_read_unlock();
- this_cpu_dec(bpf_prog_active);
- preempt_enable();
+ bpf_enable_instrumentation();
kvfree(keys);
kvfree(values);
goto alloc;
@@ -1445,8 +1442,7 @@ static int
}
rcu_read_unlock();
- this_cpu_dec(bpf_prog_active);
- preempt_enable();
+ bpf_enable_instrumentation();
if (bucket_cnt && (copy_to_user(ukeys + total * key_size, keys,
key_size * bucket_cnt) ||
copy_to_user(uvalues + total * value_size, values,
next prev parent reply other threads:[~2020-02-24 15:03 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 ` [patch V3 09/22] bpf: Dont iterate over possible CPUs with interrupts disabled Thomas Gleixner
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 ` Thomas Gleixner [this message]
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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