[RFC NEXT] mm: Fix suspicious RCU usage at kernel/sched/core.c:7318

Larry Finger
2015-06-15T21:25:33Z

Beginning at commit d52d399, the following INFO splat is logged:

[ 2.816564] ===============================
[ 2.816986] [ INFO: suspicious RCU usage. ]
[ 2.817402] 4.1.0-rc7-next-20150612 #1 Not tainted
[ 2.817881] -------------------------------
[ 2.818297] kernel/sched/core.c:7318 Illegal context switch in RCU-bh read-side critical section!
[ 2.819180]
other info that might help us debug this:

[ 2.819947]
rcu_scheduler_active = 1, debug_locks = 0
[ 2.820578] 3 locks held by systemd/1:
[ 2.820954] #0: (rtnl_mutex){+.+.+.}, at: [<ffffffff815f0c8f>] rtnetlink_rcv+0x1f/0x40
[ 2.821855] #1: (rcu_read_lock_bh){......}, at: [<ffffffff816a34e2>] ipv6_add_addr+0x62/0x540
[ 2.822808] #2: (addrconf_hash_lock){+...+.}, at: [<ffffffff816a3604>] ipv6_add_addr+0x184/0x540
[ 2.823790]
stack backtrace:
[ 2.824212] CPU: 0 PID: 1 Comm: systemd Not tainted 4.1.0-rc7-next-20150612 #1
[ 2.824932] Hardware name: TOSHIBA TECRA A50-A/TECRA A50-A, BIOS Version 4.20 04/17/2014
[ 2.825751] 0000000000000001 ffff880224e07838 ffffffff817263a4 ffffffff810ccf2a
[ 2.826560] ffff880224e08000 ffff880224e07868 ffffffff810b6827 0000000000000000
[ 2.827368] ffffffff81a445d3 00000000000004f4 ffff88022682e100 ffff880224e07898
[ 2.828177] Call Trace:
[ 2.828422] [<ffffffff817263a4>] dump_stack+0x4c/0x6e
[ 2.828937] [<ffffffff810ccf2a>] ? console_unlock+0x1ca/0x510
[ 2.829514] [<ffffffff810b6827>] lockdep_rcu_suspicious+0xe7/0x120
[ 2.830139] [<ffffffff8108cf05>] ___might_sleep+0x1d5/0x1f0
[ 2.830699] [<ffffffff8108cf6d>] __might_sleep+0x4d/0x90
[ 2.831239] [<ffffffff811f3789>] ? create_object+0x39/0x2e0
[ 2.831800] [<ffffffff811da427>] kmem_cache_alloc+0x47/0x250
[ 2.832375] [<ffffffff813c19ae>] ? find_next_zero_bit+0x1e/0x20
[ 2.832973] [<ffffffff811f3789>] create_object+0x39/0x2e0
[ 2.833515] [<ffffffff810b7eb6>] ? mark_held_locks+0x66/0x90
[ 2.834089] [<ffffffff8172efab>] ? _raw_spin_unlock_irqrestore+0x4b/0x60
[ 2.834761] [<ffffffff817193c1>] kmemleak_alloc_percpu+0x61/0xe0
[ 2.835369] [<ffffffff811a26f0>] pcpu_alloc+0x370/0x630

Additional backtrace lines are truncated. In addition, the above splat is
followed by several "BUG: sleeping function called from invalid context
at mm/slub.c:1268" outputs. As suggested by Martin KaFai Lau, these are the
clue to the fix. Routine kmemleak_alloc_percpu() always uses GFP_KERNEL
for its allocations, whereas it should use the value input to pcpu_alloc().

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
To: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org
---
include/linux/kmemleak.h | 3 ++-
mm/kmemleak.c | 9 +++++----
mm/kmemleak.c.rej | 19 +++++++++++++++++++
mm/percpu.c | 2 +-
4 files changed, 27 insertions(+), 6 deletions(-)
create mode 100644 mm/kmemleak.c.rej

diff --git a/include/linux/kmemleak.h b/include/linux/kmemleak.h
index e705467..ec4437b 100644
--- a/include/linux/kmemleak.h
+++ b/include/linux/kmemleak.h
@@ -28,7 +28,8 @@
extern void kmemleak_init(void) __ref;
extern void kmemleak_alloc(const void *ptr, size_t size, int min_count,
gfp_t gfp) __ref;
-extern void kmemleak_alloc_percpu(const void __percpu *ptr, size_t size) __ref;
+extern void kmemleak_alloc_percpu(const void __percpu *ptr, size_t size,
+ gfp_t gfp) __ref;
extern void kmemleak_free(const void *ptr) __ref;
extern void kmemleak_free_part(const void *ptr, size_t size) __ref;
extern void kmemleak_free_percpu(const void __percpu *ptr) __ref;
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index ca9e5a5..b5f5129 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -930,12 +930,13 @@ EXPORT_SYMBOL_GPL(kmemleak_alloc);
* kmemleak_alloc_percpu - register a newly allocated __percpu object
* @ptr: __percpu pointer to beginning of the object
* @size: size of the object
+ * @gfp: kmalloc() flags used for kmemleak internal memory allocations
*
* This function is called from the kernel percpu allocator when a new object
- * (memory block) is allocated (alloc_percpu). It assumes GFP_KERNEL
- * allocation.
+ * (memory block) is allocated (alloc_percpu).
*/
-void __ref kmemleak_alloc_percpu(const void __percpu *ptr, size_t size)
+void __ref kmemleak_alloc_percpu(const void __percpu *ptr, size_t size,
+ gfp_t gfp)
{
unsigned int cpu;

@@ -948,7 +949,7 @@ void __ref kmemleak_alloc_percpu(const void __percpu *ptr, size_t size)
if (kmemleak_enabled && ptr && !IS_ERR(ptr))
for_each_possible_cpu(cpu)
create_object((unsigned long)per_cpu_ptr(ptr, cpu),
- size, 0, GFP_KERNEL);
+ size, 0, gfp);
else if (kmemleak_early_log)
log_early(KMEMLEAK_ALLOC_PERCPU, ptr, size, 0);
}
diff --git a/mm/kmemleak.c.rej b/mm/kmemleak.c.rej
new file mode 100644
index 0000000..d93c2fe
--- /dev/null
+++ b/mm/kmemleak.c.rej
@@ -0,0 +1,19 @@
+--- mm/kmemleak.c
++++ mm/kmemleak.c
+@@ -930,12 +930,13 @@ EXPORT_SYMBOL_GPL(kmemleak_alloc);
+ * kmemleak_alloc_percpu - register a newly allocated __percpu object
+ * @ptr: __percpu pointer to beginning of the object
+ * @size: size of the object
++ * @gfp: kmalloc() flags used for kmemleak internal memory allocations
+ *
+ * This function is called from the kernel percpu allocator when a new object
+- * (memory block) is allocated (alloc_percpu). It assumes GFP_KERNEL
+- * allocation.
++ * (memory block) is allocated (alloc_percpu).
+ */
+-void __ref kmemleak_alloc_percpu(const void __percpu *ptr, size_t size)
++void __ref kmemleak_alloc_percpu(const void __percpu *ptr, size_t size,
++ gfp_t gfp)
+ {
+ unsigned int cpu;
+
diff --git a/mm/percpu.c b/mm/percpu.c
index dfd0248..2dd7448 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1030,7 +1030,7 @@ area_found:
memset((void *)pcpu_chunk_addr(chunk, cpu, 0) + off, 0, size);

ptr = __addr_to_pcpu_ptr(chunk->base_addr + off);
- kmemleak_alloc_percpu(ptr, size);
+ kmemleak_alloc_percpu(ptr, size, gfp);
return ptr;

fail_unlock:
--
2.1.4