futex: Fix might_sleep() warning in futex_pivot_pending()

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A younger me put a WARN in might_sleep() to warn about nested sleep loops. This
younger me also build a wait-loop variant that can deal with it. This wait-loop
variant doesn't have all the fancy wrappers, since it isn't used much. It also
lacks wait-bit support.

Add the wait-bit support and use it to fix the nested wait issue.

Fixes: 8e7ff730dd ("futex: Fix race in futex_pivot_pending() during private hash resize")
Reported-by: syzbot+350a93852ac854927f45@syzkaller.appspotmail.com
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260820074927.GH1246887@noisy.programming.kicks-ass.net
Closes: https://syzkaller.appspot.com/bug?extid=350a93852ac854927f45

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This commit is contained in:

Peter Zijlstra 2026-08-20 09:49:27 +02:00 • committed by Thomas Gleixner

parent bde0238083

commit d8aa5dd979

5 changed files with 54 additions and 4 deletions

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1

include/linux/wait.h

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1

include/linux/wait_bit.h

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27

kernel/futex/core.c

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15

kernel/sched/wait.c

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14

kernel/sched/wait_bit.c

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