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>,
John Hubbard <jhubbard@nvidia.com>,
Michel Lespinasse <walken@google.com>
Subject: [PATCH v6 07/12] mmap locking API: add mmap_read_trylock_non_owner()
Date: Tue, 19 May 2020 22:29:03 -0700 [thread overview]
Message-ID: <20200520052908.204642-8-walken@google.com> (raw)
In-Reply-To: <20200520052908.204642-1-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>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
---
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_);
}
}
--
2.26.2.761.g0e0b3e54be-goog
next prev parent reply other threads:[~2020-05-20 5:29 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-20 5:28 [PATCH v6 00/12] Add a new mmap locking API wrapping mmap_sem calls Michel Lespinasse
2020-05-20 5:28 ` [PATCH v6 01/12] mmap locking API: initial implementation as rwsem wrappers Michel Lespinasse
2020-05-20 5:28 ` [PATCH v6 02/12] MMU notifier: use the new mmap locking API Michel Lespinasse
2020-05-20 5:28 ` [PATCH v6 03/12] DMA reservations: " Michel Lespinasse
2020-05-20 5:29 ` [PATCH v6 04/12] mmap locking API: use coccinelle to convert mmap_sem rwsem call sites Michel Lespinasse
2020-05-20 5:29 ` [PATCH v6 05/12] mmap locking API: convert mmap_sem call sites missed by coccinelle Michel Lespinasse
2020-05-21 3:23 ` Andrew Morton
2020-05-21 4:49 ` Michel Lespinasse
2020-05-20 5:29 ` [PATCH v6 06/12] mmap locking API: convert nested write lock sites Michel Lespinasse
2020-05-20 5:29 ` Michel Lespinasse [this message]
2020-05-22 14:15 ` [PATCH v6 07/12] mmap locking API: add mmap_read_trylock_non_owner() Davidlohr Bueso
2020-05-20 5:29 ` [PATCH v6 08/12] mmap locking API: add MMAP_LOCK_INITIALIZER Michel Lespinasse
2020-05-29 20:17 ` Daniel Jordan
2020-05-20 5:29 ` [PATCH v6 09/12] mmap locking API: add mmap_assert_locked() and mmap_assert_write_locked() Michel Lespinasse
2020-05-21 7:35 ` Vlastimil Babka
2020-05-29 20:36 ` Daniel Jordan
2020-05-20 5:29 ` [PATCH v6 10/12] mmap locking API: rename mmap_sem to mmap_lock Michel Lespinasse
2020-05-22 14:16 ` Davidlohr Bueso
2020-05-29 20:42 ` Daniel Jordan
2020-05-20 5:29 ` [PATCH v6 11/12] mmap locking API: convert mmap_sem API comments Michel Lespinasse
2020-05-21 7:38 ` Vlastimil Babka
2020-05-22 14:13 ` Davidlohr Bueso
2020-05-29 20:50 ` Daniel Jordan
2020-05-20 5:29 ` [PATCH v6 12/12] mmap locking API: convert mmap_sem comments Michel Lespinasse
2020-05-21 3:22 ` Andrew Morton
2020-05-21 4:51 ` Michel Lespinasse
2020-05-21 7:41 ` Vlastimil Babka
2020-05-21 7:50 ` Michel Lespinasse
2020-05-21 17:25 ` Andrew Morton
2020-05-22 14:21 ` Vlastimil Babka
2020-05-29 21:16 ` Daniel Jordan
2020-06-09 12:03 ` [PATCH v6 00/12] Add a new mmap locking API wrapping mmap_sem calls Michal Hocko
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