From: Peter Xu <peterx@redhat.com>
To: linux-man@vger.kernel.org
Cc: Alejandro Colomar <alx.manpages@gmail.com>,
Nadav Amit <nadav.amit@gmail.com>,
Andrea Arcangeli <aarcange@redhat.com>,
linux-kernel@vger.kernel.org,
Michael Kerrisk <mtk.manpages@gmail.com>,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
Axel Rasmussen <axelrasmussen@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linux MM Mailing List <linux-mm@kvack.org>,
peterx@redhat.com
Subject: [PATCH v2 1/4] userfaultfd.2: Add UFFD_FEATURE_THREAD_ID docs
Date: Thu, 4 Mar 2021 11:31:37 -0500 [thread overview]
Message-ID: <20210304163140.543171-2-peterx@redhat.com> (raw)
In-Reply-To: <20210304163140.543171-1-peterx@redhat.com>
UFFD_FEATURE_THREAD_ID is supported since Linux 4.14.
Signed-off-by: Peter Xu <peterx@redhat.com>
---
man2/userfaultfd.2 | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/man2/userfaultfd.2 b/man2/userfaultfd.2
index e7dc9f813..0cd426a8a 100644
--- a/man2/userfaultfd.2
+++ b/man2/userfaultfd.2
@@ -77,6 +77,13 @@ When the last file descriptor referring to a userfaultfd object is closed,
all memory ranges that were registered with the object are unregistered
and unread events are flushed.
.\"
+.PP
+Since Linux 4.14, userfaultfd page fault message can selectively embed faulting
+thread ID information into the fault message. One needs to enable this feature
+explicitly using the
+.BR UFFD_FEATURE_THREAD_ID
+feature bit when initializing the userfaultfd context. By default, thread ID
+reporting is diabled.
.SS Usage
The userfaultfd mechanism is designed to allow a thread in a multithreaded
program to perform user-space paging for the other threads in the process.
@@ -229,6 +236,9 @@ struct uffd_msg {
struct {
__u64 flags; /* Flags describing fault */
__u64 address; /* Faulting address */
+ union {
+ __u32 ptid; /* Thread ID of the fault */
+ } feat;
} pagefault;
struct { /* Since Linux 4.11 */
@@ -358,6 +368,9 @@ otherwise it is a read fault.
.\" UFFD_PAGEFAULT_FLAG_WP is not yet supported.
.RE
.TP
+.I pagefault.feat.pid
+The thread ID that triggered the page fault.
+.TP
.I fork.ufd
The file descriptor associated with the userfault object
created for the child created by
--
2.26.2
next prev parent reply other threads:[~2021-03-04 16:34 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-04 16:31 [PATCH v2 0/4] man2: udpate mm/userfaultfd manpages to latest Peter Xu
2021-03-04 16:31 ` Peter Xu [this message]
2021-03-04 16:31 ` [PATCH v2 2/4] userfaultfd.2: Add write-protect mode Peter Xu
2021-03-10 19:16 ` Alejandro Colomar (man-pages)
2021-03-10 21:46 ` Peter Xu
2021-03-04 16:31 ` [PATCH v2 3/4] ioctl_userfaultfd.2: Add UFFD_FEATURE_THREAD_ID docs Peter Xu
2021-03-04 16:31 ` [PATCH v2 4/4] ioctl_userfaultfd.2: Add write-protect mode docs Peter Xu
2021-03-04 17:54 ` [PATCH v2 0/4] man2: udpate mm/userfaultfd manpages to latest Axel Rasmussen
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