From: Vineeth Vijayan vneethv@linux.ibm.com
stable inclusion from stable-5.10.50 commit 38a2ba82e249098fe9e21a731957a1c1e08ad0d8 bugzilla: 174522 https://gitee.com/openeuler/kernel/issues/I4DNFY
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit c749d8c018daf5fba6dfac7b6c5c78b27efd7d65 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
Signed-off-by: Chen Jun chenjun102@huawei.com Acked-by: Weilong Chen chenweilong@huawei.com Signed-off-by: Chen Jun chenjun102@huawei.com --- drivers/s390/cio/chp.c | 3 +++ 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 dfcbe54591fb..93e22785a0e0 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 fc06a4002168..93aa7eabe8b1 100644 --- a/drivers/s390/cio/chsc.c +++ b/drivers/s390/cio/chsc.c @@ -757,8 +757,6 @@ 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 */