This fixes the following sparse error when using
CONFIG_SPARSE_RCU_POINTER=y and "make C=2 fs/eventpoll.o"
fs/eventpoll.c:514:17: error: incompatible types in comparison expression (different address spaces)
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Davide Libenzi <davidel@xxxxxxxxxxxxxxx>
Cc: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Eric Wong <normalperson@xxxxxxxx>
---
Oleg: I found this error since I was working on an unrelated patch
to convert wakeup_source users to RCU in epoll. This was introduced
in:
commit 971316f0503a5c50633d07b83b6db2f15a3a5b00
(epoll: ep_unregister_pollwait() can use the freed pwq->whead)
fs/eventpoll.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 9fec183..1326409 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -228,7 +228,7 @@ struct eppoll_entry {
wait_queue_t wait;
/* The wait queue head that linked the "wait" wait queue item */
- wait_queue_head_t *whead;
+ wait_queue_head_t __rcu *whead;
};
/* Wrapper struct used by poll queueing */
@@ -929,7 +929,7 @@ static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *k
struct eventpoll *ep = epi->ep;
if ((unsigned long)key & POLLFREE) {
- ep_pwq_from_wait(wait)->whead = NULL;
+ RCU_INIT_POINTER(ep_pwq_from_wait(wait)->whead, NULL);
/*
* whead = NULL above can race with ep_remove_wait_queue()
* which can do another remove_wait_queue() after us, so we
@@ -1018,7 +1018,7 @@ static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead,
if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) {
init_waitqueue_func_entry(&pwq->wait, ep_poll_callback);
- pwq->whead = whead;
+ RCU_INIT_POINTER(pwq->whead, whead);
pwq->base = epi;
add_wait_queue(whead, &pwq->wait);
list_add_tail(&pwq->llink, &epi->pwqlist);
--
Eric Wong
--
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