[PATCH AUTOSEL 5.6 59/68] firmware: fix a double abort case with fw_load_sysfs_fallback

Sasha Levin
2020-04-10T03:47:51Z

From: Junyong Sun <sunjy516@gmail.com>

[ Upstream commit bcfbd3523f3c6eea51a74d217a8ebc5463bcb7f4 ]

fw_sysfs_wait_timeout may return err with -ENOENT
at fw_load_sysfs_fallback and firmware is already
in abort status, no need to abort again, so skip it.

This issue is caused by concurrent situation like below:
when thread 1# wait firmware loading, thread 2# may write
-1 to abort loading and wakeup thread 1# before it timeout.
so wait_for_completion_killable_timeout of thread 1# would
return remaining time which is != 0 with fw_st->status
FW_STATUS_ABORTED.And the results would be converted into
err -ENOENT in __fw_state_wait_common and transfered to
fw_load_sysfs_fallback in thread 1#.
The -ENOENT means firmware status is already at ABORTED,
so fw_load_sysfs_fallback no need to get mutex to abort again.
-----------------------------
thread 1#,wait for loading
fw_load_sysfs_fallback
->fw_sysfs_wait_timeout
->__fw_state_wait_common
->wait_for_completion_killable_timeout

in __fw_state_wait_common,
...
93 ret = wait_for_completion_killable_timeout(&fw_st->completion, timeout);
94 if (ret != 0 && fw_st->status == FW_STATUS_ABORTED)
95 return -ENOENT;
96 if (!ret)
97 return -ETIMEDOUT;
98
99 return ret < 0 ? ret : 0;
-----------------------------
thread 2#, write -1 to abort loading
firmware_loading_store
->fw_load_abort
->__fw_load_abort
->fw_state_aborted
->__fw_state_set
->complete_all

in __fw_state_set,
...
111 if (status == FW_STATUS_DONE || status == FW_STATUS_ABORTED)
112 complete_all(&fw_st->completion);
-------------------------------------------
BTW,the double abort issue would not cause kernel panic or create an issue,
but slow down it sometimes.The change is just a minor optimization.

Signed-off-by: Junyong Sun <sunjunyong@xiaomi.com>
Acked-by: Luis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/r/1583202968-28792-1-git-send-email-sunjunyong@xiaomi.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/base/firmware_loader/fallback.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/firmware_loader/fallback.c b/drivers/base/firmware_loader/fallback.c
index 8704e1bae1758..1e9c96e3ed636 100644
--- a/drivers/base/firmware_loader/fallback.c
+++ b/drivers/base/firmware_loader/fallback.c
@@ -525,7 +525,7 @@ static int fw_load_sysfs_fallback(struct fw_sysfs *fw_sysfs,
}

retval = fw_sysfs_wait_timeout(fw_priv, timeout);
- if (retval < 0) {
+ if (retval < 0 && retval != -ENOENT) {
mutex_lock(&fw_lock);
fw_load_abort(fw_sysfs);
mutex_unlock(&fw_lock);
--
2.20.1