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rseq: Prevent hard lockup on granted time slice extension

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__exit_to_user_mode_loop() invokes rseq_grant_timeslice_extension() with
interrupts enabled. If the extension is granted it invokes
hrtimer_rearm_deferred_tif() to ensure that a pending deferred hrtimer
rearm is handled before exiting to user space.

Though this invokes __hrtimer_rearm_deferred() which expects to be invoked
with interrupts disabled as it takes hrtimer_cpu_base::lock with
raw_spin_lock(). That's a livelock waiting to happen and caught by lockdep:

    WARNING: ./include/linux/hrtimer_rearm.h:17 at irqentry_exit, CPU#1: slice_test
    WARNING: inconsistent lock state
    inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.

Prevent this by disabling interrupts around the invocation of
hrtimer_rearm_deferred_tif() in rseq_grant_timeslice_extension().

[ tglx: Massaged change log ]

Fixes: 15dd3a9488 ("hrtimer: Push reprogramming timers into the interrupt return path")
Signed-off-by: Niels Pressel <npressel@ethz.ch>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260802124423.51616-1-npressel@ethz.ch
This commit is contained in:
Niels Pressel
2026-08-02 14:44:23 +02:00
committed by Thomas Gleixner
parent 075b74841b
commit ada54c2ba6
1 changed files with 1 additions and 0 deletions
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1
include/linux/rseq_entry.h
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@@ -233,6 +233,7 @@ static __always_inline bool __rseq_grant_slice_extension(bool work_pending)
static __always_inline bool rseq_grant_slice_extension(unsigned long ti_work, unsigned long mask)
{
if (unlikely(__rseq_grant_slice_extension(ti_work & mask))) {
guard(irq)();
hrtimer_rearm_deferred_tif(ti_work);
return true;
}