From: paulmck@kernel.org
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
mingo@kernel.org, jiangshanlai@gmail.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org,
"Paul E. McKenney" <paulmck@kernel.org>,
Ming Lei <ming.lei@redhat.com>, Jens Axboe <axboe@kernel.dk>
Subject: [PATCH sl-b 6/6] percpu_ref: Print stack trace upon reference-count underflow
Date: Fri, 4 Dec 2020 16:40:57 -0800 [thread overview]
Message-ID: <20201205004057.32199-6-paulmck@kernel.org> (raw)
In-Reply-To: <20201205004022.GA31166@paulmck-ThinkPad-P72>
From: "Paul E. McKenney" <paulmck@kernel.org>
In some cases, the allocator return address is in a common function, so
that more information is desired. For example, percpu_ref reference-count
underflow happens in an RCU callback function having access only
to a block of memory that is always allocated in percpu_ref_init().
This information is unhelpful.
This commit therefore causes the percpu_ref_switch_to_atomic_rcu()
function to use the new kmem_last_alloc_stack() function to collect
and print a stack trace upon reference-count underflow. This requires
the kernel use the slub allocator and be built with CONFIG_STACKTRACE=y.
As always, slub debugging must be enabled one way or another, for example,
by booting with the "slub_debug=U" kernel boot parameter.
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Reported-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
lib/percpu-refcount.c | 24 +++++++++++++++++-------
1 file changed, 17 insertions(+), 7 deletions(-)
diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c
index 8c7b21a0..ebdfa47 100644
--- a/lib/percpu-refcount.c
+++ b/lib/percpu-refcount.c
@@ -169,8 +169,6 @@ static void percpu_ref_switch_to_atomic_rcu(struct rcu_head *rcu)
struct percpu_ref *ref = data->ref;
unsigned long __percpu *percpu_count = percpu_count_ptr(ref);
unsigned long count = 0;
- void *allocaddr;
- const char *allocerr;
int cpu;
for_each_possible_cpu(cpu)
@@ -194,14 +192,26 @@ static void percpu_ref_switch_to_atomic_rcu(struct rcu_head *rcu)
atomic_long_add((long)count - PERCPU_COUNT_BIAS, &data->count);
if (atomic_long_read(&data->count) <= 0) {
- allocaddr = kmem_last_alloc(data);
+ void *allocaddr;
+ const char *allocerr;
+ void *allocstack[8];
+ int i;
+
+ allocaddr = kmem_last_alloc_stack(data, allocstack, ARRAY_SIZE(allocstack));
allocerr = kmem_last_alloc_errstring(allocaddr);
- if (allocerr)
+ if (allocerr) {
WARN_ONCE(1, "percpu ref (%ps) <= 0 (%ld) after switching to atomic (%s)",
data->release, atomic_long_read(&data->count), allocerr);
- else
- WARN_ONCE(1, "percpu ref (%ps) <= 0 (%ld) after switching to atomic (allocated at %pS)",
- data->release, atomic_long_read(&data->count), allocaddr);
+ } else {
+ pr_err("percpu ref (%ps) <= 0 (%ld) after switching to atomic (allocated at %pS)\n",
+ data->release, atomic_long_read(&data->count), allocaddr);
+ for (i = 0; i < ARRAY_SIZE(allocstack); i++) {
+ if (!allocstack[i])
+ break;
+ pr_err("\t%pS\n", allocstack[i]);
+ }
+ WARN_ON_ONCE(1);
+ }
}
/* @ref is viewed as dead on all CPUs, send out switch confirmation */
--
2.9.5
next prev parent reply other threads:[~2020-12-05 0:41 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-05 0:40 [PATCH RFC sl-b] Export return addresses for better diagnostics Paul E. McKenney
2020-12-05 0:40 ` [PATCH sl-b 1/6] mm: Add kmem_last_alloc() to return last allocation for memory block paulmck
2020-12-07 9:02 ` Joonsoo Kim
2020-12-07 17:25 ` Paul E. McKenney
2020-12-08 8:57 ` Joonsoo Kim
2020-12-08 15:17 ` Paul E. McKenney
2020-12-05 0:40 ` [PATCH sl-b 2/6] mm: Add kmem_last_alloc_errstring() to provide more kmem_last_alloc() info paulmck
2020-12-05 0:40 ` [PATCH sl-b 3/6] rcu: Make call_rcu() print allocation address of double-freed callback paulmck
2020-12-05 0:40 ` [PATCH sl-b 4/6] mm: Create kmem_last_alloc_stack() to provide stack trace in slub paulmck
2020-12-05 0:40 ` [PATCH sl-b 5/6] percpu_ref: Print allocator upon reference-count underflow paulmck
2020-12-05 0:40 ` paulmck [this message]
2020-12-09 1:11 ` [PATCH RFC v2 sl-b] Export return addresses etc. for better diagnostics Paul E. McKenney
2020-12-09 1:12 ` [PATCH v2 sl-b 1/5] mm: Add mem_dump_obj() to print source of memory block paulmck
2020-12-09 8:17 ` Christoph Hellwig
2020-12-09 14:57 ` Paul E. McKenney
2020-12-09 17:53 ` Christoph Hellwig
2020-12-09 17:59 ` Paul E. McKenney
2020-12-09 17:28 ` Vlastimil Babka
2020-12-09 23:04 ` Paul E. McKenney
2020-12-10 10:48 ` Vlastimil Babka
2020-12-10 19:56 ` Paul E. McKenney
2020-12-10 12:04 ` Joonsoo Kim
2020-12-10 23:41 ` Paul E. McKenney
2020-12-09 1:13 ` [PATCH v2 sl-b 2/5] mm: Make mem_dump_obj() handle NULL and zero-sized pointers paulmck
2020-12-09 17:48 ` Vlastimil Babka
2020-12-10 3:25 ` Paul E. McKenney
2020-12-09 1:13 ` [PATCH v2 sl-b 3/5] mm: Make mem_dump_obj() handle vmalloc() memory paulmck
2020-12-09 17:51 ` Vlastimil Babka
2020-12-09 19:39 ` Uladzislau Rezki
2020-12-09 23:23 ` Paul E. McKenney
2020-12-10 10:49 ` Vlastimil Babka
2020-12-09 19:36 ` Uladzislau Rezki
2020-12-09 19:42 ` Paul E. McKenney
2020-12-09 20:04 ` Uladzislau Rezki
2020-12-09 1:13 ` [PATCH v2 sl-b 4/5] rcu: Make call_rcu() print mem_dump_obj() info for double-freed callback paulmck
2020-12-09 1:13 ` [PATCH v2 sl-b 5/5] percpu_ref: Dump mem_dump_obj() info upon reference-count underflow paulmck
2020-12-11 1:19 ` [PATCH RFC v2 sl-b] Export return addresses etc. for better diagnostics Paul E. McKenney
2020-12-11 1:19 ` [PATCH v3 sl-b 1/6] mm: Add mem_dump_obj() to print source of memory block paulmck
2020-12-11 2:22 ` Joonsoo Kim
2020-12-11 3:33 ` Paul E. McKenney
2020-12-11 3:42 ` Paul E. McKenney
2020-12-11 6:58 ` Joonsoo Kim
2020-12-11 16:59 ` Paul E. McKenney
2020-12-11 6:54 ` Joonsoo Kim
2020-12-11 1:19 ` [PATCH v3 sl-b 2/6] mm: Make mem_dump_obj() handle NULL and zero-sized pointers paulmck
2020-12-11 1:20 ` [PATCH v3 sl-b 3/6] mm: Make mem_dump_obj() handle vmalloc() memory paulmck
2020-12-11 1:20 ` [PATCH v3 sl-b 4/6] mm: Make mem_obj_dump() vmalloc() dumps include start and length paulmck
2020-12-11 1:20 ` [PATCH v3 sl-b 5/6] rcu: Make call_rcu() print mem_dump_obj() info for double-freed callback paulmck
2020-12-11 1:20 ` [PATCH v3 sl-b 6/6] percpu_ref: Dump mem_dump_obj() info upon reference-count underflow paulmck
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