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FAILED: patch "[PATCH] io_uring: don't touch sqd->thread off tw add" failed to apply to 6.12-stable tree

PATCH [email protected] 1 participant 2 messages Jan 12, 2025

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[email protected]

author maintainer
#0 lore raw

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x bd2703b42decebdcddf76e277ba76b4c4a142d73
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025011256-extinct-expanse-d059@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From bd2703b42decebdcddf76e277ba76b4c4a142d73 Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <[email protected]>
Date: Fri, 10 Jan 2025 20:36:45 +0000
Subject: [PATCH] io_uring: don't touch sqd->thread off tw add

With IORING_SETUP_SQPOLL all requests are created by the SQPOLL task, which means that req->task should always match sqd->thread. Since accesses to sqd->thread should be separately protected, use req->task in io_req_normal_work_add() instead.

Note, in the eyes of io_req_normal_work_add(), the SQPOLL task struct is always pinned and alive, and sqd->thread can either be the task or NULL. It's only problematic if the compiler decides to reload the value after the null check, which is not so likely.

Cc [email protected]
Cc Bui Quang Minh <[email protected]>
Reported-by lizetao <[email protected]>
Fixes 78f9b61bd8e54 ("io_uring: wake SQPOLL task when task_work is added to an empty queue")
Signed-off-by Pavel Begunkov <[email protected]>
Link https://lore.kernel.org/r/1cbbe72cf32c45a8fee96026463024cd8564a7d7.1736541357.git.asml.silence@gmail.com open here
Signed-off-by Jens Axboe <[email protected]>
io_uring/io_uring.c +1 -4
index d3403c8216db..5eb119002099 100644
@@ -1226,10 +1226,7 @@ static void io_req_normal_work_add(struct io_kiocb *req)
 
 	/* SQPOLL doesn't need the task_work added, it'll run it itself */
 	if (ctx->flags & IORING_SETUP_SQPOLL) {
-		struct io_sq_data *sqd = ctx->sq_data;
-
-		if (sqd->thread)
-			__set_notify_signal(sqd->thread);
+		__set_notify_signal(tctx->task);
 		return;
 	}
author maintainer
#1 lore raw
Quoted 53 lines · On Sun, Jan 12, 2025 at 10:36:56AM +0100, [email protected] wrote:

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x bd2703b42decebdcddf76e277ba76b4c4a142d73
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025011256-extinct-expanse-d059@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

Quoted 1 line

From bd2703b42decebdcddf76e277ba76b4c4a142d73 Mon Sep 17 00:00:00 2001

From: Pavel Begunkov <[email protected]>
Date: Fri, 10 Jan 2025 20:36:45 +0000
Subject: [PATCH] io_uring: don't touch sqd->thread off tw add

With IORING_SETUP_SQPOLL all requests are created by the SQPOLL task, which means that req->task should always match sqd->thread. Since accesses to sqd->thread should be separately protected, use req->task in io_req_normal_work_add() instead.

Note, in the eyes of io_req_normal_work_add(), the SQPOLL task struct is always pinned and alive, and sqd->thread can either be the task or NULL. It's only problematic if the compiler decides to reload the value after the null check, which is not so likely.

Cc [email protected]
Cc Bui Quang Minh <[email protected]>
Reported-by lizetao <[email protected]>
Fixes 78f9b61bd8e54 ("io_uring: wake SQPOLL task when task_work is added to an empty queue")
Signed-off-by Pavel Begunkov <[email protected]>
Link https://lore.kernel.org/r/1cbbe72cf32c45a8fee96026463024cd8564a7d7.1736541357.git.asml.silence@gmail.com open here
Signed-off-by Jens Axboe <[email protected]>
io_uring/io_uring.c +0 -0
index d3403c8216db..5eb119002099 100644

io_uring/io_uring.c static void io_req_normal_work_add(struct io_kiocb *req) · line 1231

Quoted 10 lines
io_uring/io_uring.c +1 -4
@@ -1226,10 +1226,7 @@ static void io_req_normal_work_add(struct io_kiocb *req)
 
 	/* SQPOLL doesn't need the task_work added, it'll run it itself */
 	if (ctx->flags & IORING_SETUP_SQPOLL) {
-		struct io_sq_data *sqd = ctx->sq_data;
-
-		if (sqd->thread)
-			__set_notify_signal(sqd->thread);
+		__set_notify_signal(tctx->task);
 		return;
 	}

Note, this breaks the build, it applies just fine, it's just that ->task is not a valid field here :(

thanks,

greg k-h