On 2019/12/17 21:37, Takashi Iwai wrote:
On Tue, 17 Dec 2019 14:24:21 +0100,
Jia-Ju Bai wrote:
The driver may sleep while holding a read lock.
The function call path (from bottom to top) in Linux 4.19 is:
sound/core/seq/seq_memory.c, 96:
copy_from_user in snd_seq_dump_var_event
sound/core/seq/seq_virmidi.c, 97:
snd_seq_dump_var_event in snd_virmidi_dev_receive_event
sound/core/seq/seq_virmidi.c, 88:
_raw_read_lock in snd_virmidi_dev_receive_event
This can't happen. snd_virmidi_dev_receive_event() takes
conditionally either read_lock or rw_sem depending on the atomic
argument. And the data including user-space pointer is handled always
with atomic=1, hence down_read() is used instead of read_lock() here.
Okay, thanks for the explanation.
Best wishes,
Jia-Ju Bai
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