diff options
Diffstat (limited to 'debian/patches-rt/0315-userfaultfd-Use-a-seqlock-instead-of-seqcount.patch')
| -rw-r--r-- | debian/patches-rt/0315-userfaultfd-Use-a-seqlock-instead-of-seqcount.patch | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/debian/patches-rt/0315-userfaultfd-Use-a-seqlock-instead-of-seqcount.patch b/debian/patches-rt/0315-userfaultfd-Use-a-seqlock-instead-of-seqcount.patch new file mode 100644 index 000000000..227e20afd --- /dev/null +++ b/debian/patches-rt/0315-userfaultfd-Use-a-seqlock-instead-of-seqcount.patch @@ -0,0 +1,80 @@ +From 4639984350d5520c7268c26b6454c2f47cf139e4 Mon Sep 17 00:00:00 2001 +From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Date: Wed, 18 Dec 2019 12:25:09 +0100 +Subject: [PATCH 315/347] userfaultfd: Use a seqlock instead of seqcount +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.246-rt110.tar.xz + +[ 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: Steven Rostedt (VMware) <rostedt@goodmis.org> +--- + fs/userfaultfd.c | 12 ++++++------ + 1 file changed, 6 insertions(+), 6 deletions(-) + +diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c +index 23c8efc967af..3f79609511da 100644 +--- a/fs/userfaultfd.c ++++ b/fs/userfaultfd.c +@@ -56,7 +56,7 @@ 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 */ +@@ -1059,7 +1059,7 @@ 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 +@@ -1085,7 +1085,7 @@ 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; +@@ -1258,11 +1258,11 @@ 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); + } +@@ -1936,7 +1936,7 @@ 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); + } + + SYSCALL_DEFINE1(userfaultfd, int, flags) +-- +2.36.1 + |