(adding Colin and John)
On 09/09/2015 12:41 AM, Shawn Lin wrote:
we found this issue but still exit in lastest kernel. Simply
keep ion_handle_create under mutex_lock to avoid this race.
WARNING: CPU: 2 PID: 2648 at drivers/staging/android/ion/ion.c:512 ion_handle_add+0xb4/0xc0()
ion_handle_add: buffer already found.
Modules linked in: iwlmvm iwlwifi mac80211 cfg80211 compat
CPU: 2 PID: 2648 Comm: TimedEventQueue Tainted: G W 3.14.0 #7
00000000 00000000 9a3efd2c 80faf273 9a3efd6c 9a3efd5c 80935dc9 811d7fd3
9a3efd88 00000a58 812208a0 00000200 80e128d4 80e128d4 8d4ae00c a8cd8600
a8cd8094 9a3efd74 80935e0e 00000009 9a3efd6c 811d7fd3 9a3efd88 9a3efd9c
Call Trace:
[<80faf273>] dump_stack+0x48/0x69
[<80935dc9>] warn_slowpath_common+0x79/0x90
[<80e128d4>] ? ion_handle_add+0xb4/0xc0
[<80e128d4>] ? ion_handle_add+0xb4/0xc0
[<80935e0e>] warn_slowpath_fmt+0x2e/0x30
[<80e128d4>] ion_handle_add+0xb4/0xc0
[<80e144cc>] ion_import_dma_buf+0x8c/0x110
[<80c517c4>] reg_init+0x364/0x7d0
[<80993363>] ? futex_wait+0x123/0x210
[<80992e0e>] ? get_futex_key+0x16e/0x1e0
[<8099308f>] ? futex_wake+0x5f/0x120
[<80c51e19>] vpu_service_ioctl+0x1e9/0x500
[<80994aec>] ? do_futex+0xec/0x8e0
[<80971080>] ? prepare_to_wait_event+0xc0/0xc0
[<80c51c30>] ? reg_init+0x7d0/0x7d0
[<80a22562>] do_vfs_ioctl+0x2d2/0x4c0
[<80b198ad>] ? inode_has_perm.isra.41+0x2d/0x40
[<80b199cf>] ? file_has_perm+0x7f/0x90
[<80b1a5f7>] ? selinux_file_ioctl+0x47/0xf0
[<80a227a8>] SyS_ioctl+0x58/0x80
[<80fb45e8>] syscall_call+0x7/0x7
[<80fb0000>] ? mmc_do_calc_max_discard+0xab/0xe4
Fixes: 83271f626 ("ion: hold reference to handle...")
Signed-off-by: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>
---
drivers/staging/android/ion/ion.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c
index eec878e..32e7b5c 100644
--- a/drivers/staging/android/ion/ion.c
+++ b/drivers/staging/android/ion/ion.c
@@ -1179,13 +1179,13 @@ struct ion_handle *ion_import_dma_buf(struct ion_client *client, int fd)
mutex_unlock(&client->lock);
goto end;
}
- mutex_unlock(&client->lock);
handle = ion_handle_create(client, buffer);
- if (IS_ERR(handle))
+ if (IS_ERR(handle)) {
+ mutex_unlock(&client->lock);
goto end;
+ }
- mutex_lock(&client->lock);
ret = ion_handle_add(client, handle);
mutex_unlock(&client->lock);
if (ret) {
So the patch looks correct but the locking change there seems like it was added
deliberately. Colin/John, do you remember why the locking for ion_import_dma_buf
changed? Was there a deadlock condition somewhere?
Thanks,
Laura
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