From 5853cc2a89f726e21d51ca0fd75757a03126a84b Mon Sep 17 00:00:00 2001 From: Colin Cross Date: Tue, 7 May 2013 17:52:05 +0000 Subject: [PATCH] freezer: add unsafe versions of freezable helpers for CIFS CIFS calls wait_event_freezekillable_unsafe with a VFS lock held, which is unsafe and will cause lockdep warnings when 6aa9707 "lockdep: check that no locks held at freeze time" is reapplied (it was reverted in dbf520a). CIFS shouldn't be doing this, but it has long-running syscalls that must hold a lock but also shouldn't block suspend. Until CIFS freeze handling is rewritten to use a signal to exit out of the critical section, add a new wait_event_freezekillable_unsafe helper that will not run the lockdep test when 6aa9707 is reapplied, and call it from CIFS. In practice the likley result of holding the lock while freezing is that a second task blocked on the lock will never freeze, aborting suspend, but it is possible to manufacture a case using the cgroup freezer, the lock, and the suspend freezer to create a deadlock. Silencing the lockdep warning here will allow problems to be found in other drivers that may have a more serious deadlock risk, and prevent new problems from being added. Acked-by: Pavel Machek Acked-by: Tejun Heo Reviewed-by: Jeff Layton Signed-off-by: Colin Cross Signed-off-by: Rafael J. Wysocki --- fs/cifs/transport.c | 2 +- include/linux/freezer.h | 13 +++++++++++++ 2 files changed, 14 insertions(+), 1 deletion(-) diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c index bfbf4700d16..b70aa7c9139 100644 --- a/fs/cifs/transport.c +++ b/fs/cifs/transport.c @@ -447,7 +447,7 @@ wait_for_response(struct TCP_Server_Info *server, struct mid_q_entry *midQ) { int error; - error = wait_event_freezekillable(server->response_q, + error = wait_event_freezekillable_unsafe(server->response_q, midQ->mid_state != MID_REQUEST_SUBMITTED); if (error < 0) return -ERESTARTSYS; diff --git a/include/linux/freezer.h b/include/linux/freezer.h index 5b31e21c485..d3c038ec9a8 100644 --- a/include/linux/freezer.h +++ b/include/linux/freezer.h @@ -212,6 +212,16 @@ static inline bool freezer_should_skip(struct task_struct *p) __retval; \ }) +/* DO NOT ADD ANY NEW CALLERS OF THIS FUNCTION */ +#define wait_event_freezekillable_unsafe(wq, condition) \ +({ \ + int __retval; \ + freezer_do_not_count(); \ + __retval = wait_event_killable(wq, (condition)); \ + freezer_count_unsafe(); \ + __retval; \ +}) + #define wait_event_freezable(wq, condition) \ ({ \ int __retval; \ @@ -277,6 +287,9 @@ static inline void set_freezable(void) {} #define wait_event_freezekillable(wq, condition) \ wait_event_killable(wq, condition) +#define wait_event_freezekillable_unsafe(wq, condition) \ + wait_event_killable(wq, condition) + #endif /* !CONFIG_FREEZER */ #endif /* FREEZER_H_INCLUDED */ -- 2.41.0