From: Michel Lespinasse <walken@google.com>
To: Andrew Morton <akpm@linux-foundation.org>, linux-mm <linux-mm@kvack.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Laurent Dufour <ldufour@linux.ibm.com>,
Vlastimil Babka <vbabka@suse.cz>,
Matthew Wilcox <willy@infradead.org>,
Liam Howlett <Liam.Howlett@oracle.com>,
Jerome Glisse <jglisse@redhat.com>,
Davidlohr Bueso <dave@stgolabs.net>,
David Rientjes <rientjes@google.com>,
Hugh Dickins <hughd@google.com>, Ying Han <yinghan@google.com>,
Jason Gunthorpe <jgg@ziepe.ca>,
Daniel Jordan <daniel.m.jordan@oracle.com>,
Michel Lespinasse <walken@google.com>
Subject: [PATCH v5 07/10] mmap locking API: add mmap_read_trylock_non_owner()
Date: Tue, 21 Apr 2020 17:14:19 -0700 [thread overview]
Message-ID: <20200422001422.232330-8-walken@google.com> (raw)
In-Reply-To: <20200422001422.232330-1-walken@google.com>
Add a couple APIs used by kernel/bpf/stackmap.c only:
- mmap_read_trylock_non_owner()
- mmap_read_unlock_non_owner() (may be called from a work queue).
It's still not ideal that bpf/stackmap subverts the lock ownership
in this way. Thanks to Peter Zijlstra for suggesting this API as the
least-ugly way of addressing this in the short term.
Signed-off-by: Michel Lespinasse <walken@google.com>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
---
include/linux/mmap_lock.h | 14 ++++++++++++++
kernel/bpf/stackmap.c | 17 +++++------------
2 files changed, 19 insertions(+), 12 deletions(-)
diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h
index a757cb30ae77..d1826ce42f00 100644
--- a/include/linux/mmap_lock.h
+++ b/include/linux/mmap_lock.h
@@ -56,4 +56,18 @@ static inline void mmap_read_unlock(struct mm_struct *mm)
up_read(&mm->mmap_sem);
}
+static inline bool mmap_read_trylock_non_owner(struct mm_struct *mm)
+{
+ if (down_read_trylock(&mm->mmap_sem)) {
+ rwsem_release(&mm->mmap_sem.dep_map, _RET_IP_);
+ return true;
+ }
+ return false;
+}
+
+static inline void mmap_read_unlock_non_owner(struct mm_struct *mm)
+{
+ up_read_non_owner(&mm->mmap_sem);
+}
+
#endif /* _LINUX_MMAP_LOCK_H */
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 11d41f0c7005..998968659892 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -33,7 +33,7 @@ struct bpf_stack_map {
/* irq_work to run up_read() for build_id lookup in nmi context */
struct stack_map_irq_work {
struct irq_work irq_work;
- struct rw_semaphore *sem;
+ struct mm_struct *mm;
};
static void do_up_read(struct irq_work *entry)
@@ -44,8 +44,7 @@ static void do_up_read(struct irq_work *entry)
return;
work = container_of(entry, struct stack_map_irq_work, irq_work);
- up_read_non_owner(work->sem);
- work->sem = NULL;
+ mmap_read_unlock_non_owner(work->mm);
}
static DEFINE_PER_CPU(struct stack_map_irq_work, up_read_work);
@@ -317,7 +316,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
* with build_id.
*/
if (!user || !current || !current->mm || irq_work_busy ||
- mmap_read_trylock(current->mm) == 0) {
+ !mmap_read_trylock_non_owner(current->mm)) {
/* cannot access current->mm, fall back to ips */
for (i = 0; i < trace_nr; i++) {
id_offs[i].status = BPF_STACK_BUILD_ID_IP;
@@ -342,16 +341,10 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
}
if (!work) {
- mmap_read_unlock(current->mm);
+ mmap_read_unlock_non_owner(current->mm);
} else {
- work->sem = ¤t->mm->mmap_sem;
+ work->mm = current->mm;
irq_work_queue(&work->irq_work);
- /*
- * The irq_work will release the mmap_sem with
- * up_read_non_owner(). The rwsem_release() is called
- * here to release the lock from lockdep's perspective.
- */
- rwsem_release(¤t->mm->mmap_sem.dep_map, _RET_IP_);
}
}
--
2.26.1.301.g55bc3eb7cb9-goog
next prev parent reply other threads:[~2020-04-22 0:14 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-22 0:14 [PATCH v5 00/10] Add a new mmap locking API wrapping mmap_sem calls Michel Lespinasse
2020-04-22 0:14 ` [PATCH v5 01/10] mmap locking API: initial implementation as rwsem wrappers Michel Lespinasse
2020-05-18 9:28 ` Vlastimil Babka
2020-05-18 13:18 ` Laurent Dufour
2020-04-22 0:14 ` [PATCH v5 02/10] MMU notifier: use the new mmap locking API Michel Lespinasse
2020-05-18 9:28 ` Vlastimil Babka
2020-05-18 13:19 ` Laurent Dufour
2020-04-22 0:14 ` [PATCH v5 03/10] DMA reservations: " Michel Lespinasse
2020-05-18 9:30 ` Vlastimil Babka
2020-05-18 13:20 ` Laurent Dufour
2020-04-22 0:14 ` [PATCH v5 04/10] mmap locking API: use coccinelle to convert mmap_sem rwsem call sites Michel Lespinasse
2020-05-18 9:36 ` Vlastimil Babka
2020-05-18 13:21 ` Laurent Dufour
2020-04-22 0:14 ` [PATCH v5 05/10] mmap locking API: convert mmap_sem call sites missed by coccinelle Michel Lespinasse
2020-05-18 9:44 ` Vlastimil Babka
2020-05-18 13:23 ` Laurent Dufour
2020-04-22 0:14 ` [PATCH v5 06/10] mmap locking API: convert nested write lock sites Michel Lespinasse
2020-05-18 10:32 ` Vlastimil Babka
2020-05-19 12:54 ` Michel Lespinasse
2020-05-18 13:24 ` Laurent Dufour
2020-04-22 0:14 ` Michel Lespinasse [this message]
2020-05-18 10:42 ` [PATCH v5 07/10] mmap locking API: add mmap_read_trylock_non_owner() Vlastimil Babka
2020-04-22 0:14 ` [PATCH v5 08/10] mmap locking API: add MMAP_LOCK_INITIALIZER Michel Lespinasse
2020-05-18 10:45 ` Vlastimil Babka
2020-05-19 12:56 ` Michel Lespinasse
2020-05-18 13:33 ` Laurent Dufour
2020-04-22 0:14 ` [PATCH v5 09/10] mmap locking API: add mmap_assert_locked Michel Lespinasse
2020-04-22 2:10 ` Michel Lespinasse
2020-04-22 2:18 ` Matthew Wilcox
2020-04-24 1:44 ` Michel Lespinasse
2020-04-22 0:14 ` [PATCH v5 10/10] mmap locking API: rename mmap_sem to mmap_lock Michel Lespinasse
2020-04-22 1:58 ` Matthew Wilcox
2020-04-22 22:54 ` Michel Lespinasse
2020-04-23 1:59 ` Matthew Wilcox
2020-04-24 1:26 ` Michel Lespinasse
2020-04-24 1:38 ` [PATCH v5.5 09/10] mmap locking API: add mmap_assert_locked() and mmap_assert_write_locked() Michel Lespinasse
2020-05-18 11:01 ` Vlastimil Babka
2020-05-19 13:06 ` Michel Lespinasse
2020-04-24 1:39 ` [PATCH v5.5 10/10] mmap locking API: rename mmap_sem to mmap_lock Michel Lespinasse
2020-05-18 11:07 ` Vlastimil Babka
2020-05-19 13:12 ` Michel Lespinasse
2020-05-18 13:45 ` Laurent Dufour
2020-05-19 13:10 ` Michel Lespinasse
2020-05-19 13:20 ` Laurent Dufour
2020-05-19 15:32 ` Matthew Wilcox
2020-05-19 18:14 ` John Hubbard
2020-05-20 2:39 ` Michel Lespinasse
2020-05-20 7:32 ` John Hubbard
2020-05-20 8:02 ` Michel Lespinasse
2020-05-20 12:48 ` Jason Gunthorpe
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