From: zanussi@kernel.org
To: LKML <linux-kernel@vger.kernel.org>,
linux-rt-users <linux-rt-users@vger.kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@linutronix.de>,
Carsten Emde <C.Emde@osadl.org>, John Kacur <jkacur@redhat.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Daniel Wagner <wagi@monom.org>, Tom Zanussi <zanussi@kernel.org>
Cc: stable-rt@vger.kernel.org
Subject: [PATCH RT 1/8] userfaultfd: Use a seqlock instead of seqcount
Date: Mon, 9 Mar 2020 14:47:46 -0500 [thread overview]
Message-ID: <ef275aaeea4c9c1a75514eed061e29cb78a929c3.1583783251.git.zanussi@kernel.org> (raw)
In-Reply-To: <cover.1583783251.git.zanussi@kernel.org>
In-Reply-To: <cover.1583783251.git.zanussi@kernel.org>
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
v4.14.172-rt78-rc1 stable review patch.
If anyone has any objections, please let me know.
-----------
[ Upstream commit dc952a564d02997330654be9628bbe97ba2a05d3 ]
On RT write_seqcount_begin() disables preemption which leads to warning
in add_wait_queue() while the spinlock_t is acquired.
The waitqueue can't be converted to swait_queue because
userfaultfd_wake_function() is used as a custom wake function.
Use seqlock instead seqcount to avoid the preempt_disable() section
during add_wait_queue().
Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
---
fs/userfaultfd.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index e2b2196fd9428..71886a8e8f71b 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -51,7 +51,7 @@ struct userfaultfd_ctx {
/* waitqueue head for events */
wait_queue_head_t event_wqh;
/* a refile sequence protected by fault_pending_wqh lock */
- struct seqcount refile_seq;
+ seqlock_t refile_seq;
/* pseudo fd refcounting */
atomic_t refcount;
/* userfaultfd syscall flags */
@@ -1047,7 +1047,7 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait,
* waitqueue could become empty if this is the
* only userfault.
*/
- write_seqcount_begin(&ctx->refile_seq);
+ write_seqlock(&ctx->refile_seq);
/*
* The fault_pending_wqh.lock prevents the uwq
@@ -1073,7 +1073,7 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait,
list_del(&uwq->wq.entry);
__add_wait_queue(&ctx->fault_wqh, &uwq->wq);
- write_seqcount_end(&ctx->refile_seq);
+ write_sequnlock(&ctx->refile_seq);
/* careful to always initialize msg if ret == 0 */
*msg = uwq->msg;
@@ -1246,11 +1246,11 @@ static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx,
* sure we've userfaults to wake.
*/
do {
- seq = read_seqcount_begin(&ctx->refile_seq);
+ seq = read_seqbegin(&ctx->refile_seq);
need_wakeup = waitqueue_active(&ctx->fault_pending_wqh) ||
waitqueue_active(&ctx->fault_wqh);
cond_resched();
- } while (read_seqcount_retry(&ctx->refile_seq, seq));
+ } while (read_seqretry(&ctx->refile_seq, seq));
if (need_wakeup)
__wake_userfault(ctx, range);
}
@@ -1915,7 +1915,7 @@ static void init_once_userfaultfd_ctx(void *mem)
init_waitqueue_head(&ctx->fault_wqh);
init_waitqueue_head(&ctx->event_wqh);
init_waitqueue_head(&ctx->fd_wqh);
- seqcount_init(&ctx->refile_seq);
+ seqlock_init(&ctx->refile_seq);
}
/**
--
2.14.1
next prev parent reply other threads:[~2020-03-09 19:48 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-09 19:47 [PATCH RT 0/8] Linux v4.14.172-rt78-rc1 zanussi
2020-03-09 19:47 ` zanussi [this message]
2020-03-09 19:47 ` [PATCH RT 2/8] sched: migrate_enable: Use per-cpu cpu_stop_work zanussi
2020-03-09 19:47 ` [PATCH RT 3/8] sched: migrate_enable: Remove __schedule() call zanussi
2020-03-09 19:47 ` [PATCH RT 4/8] mm/memcontrol: Move misplaced local_unlock_irqrestore() zanussi
2020-03-09 19:47 ` [PATCH RT 5/8] locallock: Include header for the `current' macro zanussi
2020-03-09 19:47 ` [PATCH RT 6/8] drm/vmwgfx: Drop preempt_disable() in vmw_fifo_ping_host() zanussi
2020-03-09 19:47 ` [PATCH RT 7/8] tracing: make preempt_lazy and migrate_disable counter smaller zanussi
2020-03-09 19:47 ` [PATCH RT 8/8] Linux 4.14.172-rt78-rc1 zanussi
-- strict thread matches above, loose matches on Subject: below --
2020-03-06 18:40 [PATCH RT 0/8] Linux 4.19.106-rt45-rc1 Steven Rostedt
2020-03-06 18:40 ` [PATCH RT 1/8] userfaultfd: Use a seqlock instead of seqcount Steven Rostedt
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