s/epoll: robustify irq safety with lockdep_assert_irqs_enabled()

Sprinkle lockdep_assert_irqs_enabled() checks in the functions that do not
save and restore interrupts when dealing with the ep->wq.lock.  These are
ep_scan_ready_list() and those called by epoll_ctl(): ep_insert, ep_modify
and ep_remove.

[akpm@linux-foundation.org: remove too-obvious comments]
Link: http://lkml.kernel.org/r/20180721183127.3busfa335zlcjeox@linux-r8p5
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 1b1abc461fc03190ba3ea888bdbf27d26c9d58d0..58b96d8a898a2fb17f9f19e9068dc3272cbb443e 100644 (file)
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -670,6 +670,8 @@ static __poll_t ep_scan_ready_list(struct eventpoll *ep,
        struct epitem *epi, *nepi;
        LIST_HEAD(txlist);
 
+       lockdep_assert_irqs_enabled();
+
        /*
         * We need to lock this because we could be hit by
         * eventpoll_release_file() and epoll_ctl().
@@ -764,6 +766,8 @@ static int ep_remove(struct eventpoll *ep, struct epitem *epi)
 {
        struct file *file = epi->ffd.file;
 
+       lockdep_assert_irqs_enabled();
+
        /*
         * Removes poll wait queue hooks.
         */
@@ -1412,6 +1416,8 @@ static int ep_insert(struct eventpoll *ep, const struct epoll_event *event,
        struct epitem *epi;
        struct ep_pqueue epq;
 
+       lockdep_assert_irqs_enabled();
+
        user_watches = atomic_long_read(&ep->user->epoll_watches);
        if (unlikely(user_watches >= max_user_watches))
                return -ENOSPC;
@@ -1540,6 +1546,8 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi,
        int pwake = 0;
        poll_table pt;
 
+       lockdep_assert_irqs_enabled();
+
        init_poll_funcptr(&pt, NULL);
 
        /*