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Revert "um: work around sched_yield not yielding in time-travel mode"

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This reverts commit da780c4a07 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/8ce0b6056a9726e540f61bce77311278654219eb.camel@sipsolutions.net/
Cc: <stable@vger.kernel.org> # 6.12.y
Cc: Benjamin Berg <benjamin.berg@intel.com>
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Christian Lamparter
2025-05-09 11:50:39 +02:00
committed by Greg Kroah-Hartman
parent cd010271a9
commit 6aac2c5476
2 changed files with 0 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
arch/um/include/linux/time-internal.h
View File

@@ -83,8 +83,6 @@ extern void time_travel_not_configured(void);
#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.

11
arch/um/kernel/skas/syscall.c
View File

@@ -31,17 +31,6 @@ void handle_syscall(struct uml_pt_regs *r)
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);