This is a note to let you know that I've just added the patch titled
[PATCH 6.12] Revert "um: work around sched_yield not yielding in
time-travel mode"
to the 6.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
revert-um-work-around-sched_yield-not-yielding-in-time-travel-mode.patch
and it can be found in the queue-6.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From [email protected] Mon May 12 13:25:04 2025
From: Christian Lamparter <[email protected]>
Date: Fri, 9 May 2025 11:50:39 +0200
Subject: [PATCH 6.12] Revert "um: work around sched_yield not yielding in
time-travel mode"
To: [email protected], [email protected]
Cc: [email protected], [email protected], [email protected],
[email protected], [email protected]
Message-ID: <[email protected]>
From: Christian Lamparter <[email protected]>
This reverts commit da780c4a075ba2deb05ae29f0af4a990578c7901 which is
commit 887c5c12e80c8424bd471122d2e8b6b462e12874 upstream.
Reason being that the patch depends on at least commit 0b8b2668f998
("um: insert scheduler ticks when userspace does not yield") in order to
build. Otherwise it fails with:
| /usr/bin/ld: arch/um/kernel/skas/syscall.o: in function `handle_syscall':
| linux-6.12.27/arch/um/kernel/skas/syscall.c:43:(.text+0xa2): undefined
| reference to `tt_extra_sched_jiffies'
| collect2: error: ld returned 1 exit status
The author Benjamin Berg commented: "I think it is better to just not
backport commit 0b8b2668f998 ("um: insert scheduler ticks when userspace
does not yield")"
Link:
https://lore.kernel.org/linux-um/[email protected]/
Cc: <[email protected]> # 6.12.y
Cc: Benjamin Berg <[email protected]>
Signed-off-by: Christian Lamparter <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
arch/um/include/linux/time-internal.h | 2 --
arch/um/kernel/skas/syscall.c | 11 -----------
2 files changed, 13 deletions(-)
--- a/arch/um/include/linux/time-internal.h
+++ b/arch/um/include/linux/time-internal.h
@@ -83,8 +83,6 @@ extern void time_travel_not_configured(v
#define time_travel_del_event(...) time_travel_not_configured()
#endif /* CONFIG_UML_TIME_TRAVEL_SUPPORT */
-extern unsigned long tt_extra_sched_jiffies;
-
/*
* Without CONFIG_UML_TIME_TRAVEL_SUPPORT this is a linker error if used,
* which is intentional since we really shouldn't link it in that case.
--- a/arch/um/kernel/skas/syscall.c
+++ b/arch/um/kernel/skas/syscall.c
@@ -31,17 +31,6 @@ void handle_syscall(struct uml_pt_regs *
goto out;
syscall = UPT_SYSCALL_NR(r);
-
- /*
- * If no time passes, then sched_yield may not actually yield, causing
- * broken spinlock implementations in userspace (ASAN) to hang for long
- * periods of time.
- */
- if ((time_travel_mode == TT_MODE_INFCPU ||
- time_travel_mode == TT_MODE_EXTERNAL) &&
- syscall == __NR_sched_yield)
- tt_extra_sched_jiffies += 1;
-
if (syscall >= 0 && syscall < __NR_syscalls) {
unsigned long ret = EXECUTE_SYSCALL(syscall, regs);
Patches currently in stable-queue which might be from [email protected] are
queue-6.12/revert-um-work-around-sched_yield-not-yielding-in-time-travel-mode.patch
