84 lines
3.1 KiB
Diff
84 lines
3.1 KiB
Diff
From b76ddf8d3da1a33cc7c81c4459cf26c4741cf5e2 Mon Sep 17 00:00:00 2001
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Message-Id: <b76ddf8d3da1a33cc7c81c4459cf26c4741cf5e2.1601675153.git.zanussi@kernel.org>
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In-Reply-To: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org>
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References: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org>
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Date: Wed, 18 Dec 2019 12:25:09 +0100
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Subject: [PATCH 315/333] userfaultfd: Use a seqlock instead of seqcount
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.148-rt64.tar.xz
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[ Upstream commit dc952a564d02997330654be9628bbe97ba2a05d3 ]
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On RT write_seqcount_begin() disables preemption which leads to warning
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in add_wait_queue() while the spinlock_t is acquired.
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The waitqueue can't be converted to swait_queue because
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userfaultfd_wake_function() is used as a custom wake function.
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Use seqlock instead seqcount to avoid the preempt_disable() section
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during add_wait_queue().
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Cc: stable-rt@vger.kernel.org
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
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---
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fs/userfaultfd.c | 12 ++++++------
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1 file changed, 6 insertions(+), 6 deletions(-)
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diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
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index d269d1139f7f..ff6be687f68e 100644
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--- a/fs/userfaultfd.c
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+++ b/fs/userfaultfd.c
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@@ -61,7 +61,7 @@ struct userfaultfd_ctx {
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/* waitqueue head for events */
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wait_queue_head_t event_wqh;
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/* a refile sequence protected by fault_pending_wqh lock */
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- struct seqcount refile_seq;
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+ seqlock_t refile_seq;
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/* pseudo fd refcounting */
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atomic_t refcount;
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/* userfaultfd syscall flags */
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@@ -1064,7 +1064,7 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait,
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* waitqueue could become empty if this is the
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* only userfault.
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*/
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- write_seqcount_begin(&ctx->refile_seq);
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+ write_seqlock(&ctx->refile_seq);
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/*
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* The fault_pending_wqh.lock prevents the uwq
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@@ -1090,7 +1090,7 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait,
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list_del(&uwq->wq.entry);
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add_wait_queue(&ctx->fault_wqh, &uwq->wq);
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- write_seqcount_end(&ctx->refile_seq);
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+ write_sequnlock(&ctx->refile_seq);
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/* careful to always initialize msg if ret == 0 */
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*msg = uwq->msg;
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@@ -1263,11 +1263,11 @@ static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx,
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* sure we've userfaults to wake.
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*/
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do {
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- seq = read_seqcount_begin(&ctx->refile_seq);
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+ seq = read_seqbegin(&ctx->refile_seq);
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need_wakeup = waitqueue_active(&ctx->fault_pending_wqh) ||
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waitqueue_active(&ctx->fault_wqh);
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cond_resched();
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- } while (read_seqcount_retry(&ctx->refile_seq, seq));
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+ } while (read_seqretry(&ctx->refile_seq, seq));
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if (need_wakeup)
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__wake_userfault(ctx, range);
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}
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@@ -1938,7 +1938,7 @@ static void init_once_userfaultfd_ctx(void *mem)
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init_waitqueue_head(&ctx->fault_wqh);
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init_waitqueue_head(&ctx->event_wqh);
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init_waitqueue_head(&ctx->fd_wqh);
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- seqcount_init(&ctx->refile_seq);
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+ seqlock_init(&ctx->refile_seq);
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}
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SYSCALL_DEFINE1(userfaultfd, int, flags)
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--
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2.17.1
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