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| author | Vineeth Vijayan <vneethv@linux.ibm.com> | 2021-06-09 10:21:08 +0300 |
|---|---|---|
| committer | Vasily Gorbik <gor@linux.ibm.com> | 2021-06-18 17:41:19 +0300 |
| commit | c749d8c018daf5fba6dfac7b6c5c78b27efd7d65 (patch) | |
| tree | 6cdbb4782c6625585b0893b929c416f03116cba0 /drivers/s390 | |
| parent | 4aca3ab45d725fe8c4d8be6b67c904c3c3cc6a1d (diff) | |
| download | linux-c749d8c018daf5fba6dfac7b6c5c78b27efd7d65.tar.xz | |
s390/cio: dont call css_wait_for_slow_path() inside a lock
Currently css_wait_for_slow_path() gets called inside the chp->lock.
The path-verification-loop of slowpath inside this lock could lead to
deadlock as reported by the lockdep validator.
The ccw_device_get_chp_desc() during the instance of a device-set-online
would try to acquire the same 'chp->lock' to read the chp->desc.
The instance of this function can get called from multiple scenario,
like probing or setting-device online manually. This could, in some
corner-cases lead to the deadlock.
lockdep validator reported this as,
CPU0 CPU1
---- ----
lock(&chp->lock);
lock(kn->active#43);
lock(&chp->lock);
lock((wq_completion)cio);
The chp->lock was introduced to serialize the access of struct
channel_path. This lock is not needed for the css_wait_for_slow_path()
function, so invoke the slow-path function outside this lock.
Fixes: b730f3a93395 ("[S390] cio: add lock to struct channel_path")
Cc: <stable@vger.kernel.org>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Diffstat (limited to 'drivers/s390')
| -rw-r--r-- | drivers/s390/cio/chp.c | 3 | ||||
| -rw-r--r-- | drivers/s390/cio/chsc.c | 2 |
2 files changed, 3 insertions, 2 deletions
diff --git a/drivers/s390/cio/chp.c b/drivers/s390/cio/chp.c index e42113825415..1097e76982a5 100644 --- a/drivers/s390/cio/chp.c +++ b/drivers/s390/cio/chp.c @@ -255,6 +255,9 @@ static ssize_t chp_status_write(struct device *dev, if (!num_args) return count; + /* Wait until previous actions have settled. */ + css_wait_for_slow_path(); + if (!strncasecmp(cmd, "on", 2) || !strcmp(cmd, "1")) { mutex_lock(&cp->lock); error = s390_vary_chpid(cp->chpid, 1); diff --git a/drivers/s390/cio/chsc.c b/drivers/s390/cio/chsc.c index c22d9ee27ba1..297fb399363c 100644 --- a/drivers/s390/cio/chsc.c +++ b/drivers/s390/cio/chsc.c @@ -801,8 +801,6 @@ int chsc_chp_vary(struct chp_id chpid, int on) { struct channel_path *chp = chpid_to_chp(chpid); - /* Wait until previous actions have settled. */ - css_wait_for_slow_path(); /* * Redo PathVerification on the devices the chpid connects to */ |