linux-kernel - Re: Several tst-robust* tests time out with recent Linux kernel

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Date:   Tue, 14 Nov 2023 17:43:20 +0100
From:   Florian Weimer <fweimer@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Xi Ruoyao <xry111@...111.site>, libc-alpha@...rceware.org,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        linux-mm@...ck.org, linux-arch@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        André Almeida <andrealmeid@...lia.com>
Subject: Re: Several tst-robust* tests time out with recent Linux kernel

* Peter Zijlstra:

>> diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h
>> index b5379c0e6d6d..1a1f9301251f 100644
>> --- a/kernel/futex/futex.h
>> +++ b/kernel/futex/futex.h
>> @@ -17,7 +17,7 @@
>>   * restarts.
>>   */
>>  #ifdef CONFIG_MMU
>> -# define FLAGS_SHARED		0x01
>> +# define FLAGS_SHARED		0x10
>>  #else
>>  /*
>>   * NOMMU does not have per process address space. Let the compiler optimize
>
> Just the above seems sufficient.

There are a few futex_wake calls which hard-code the flags argument as
1:

kernel/futex/core.c=637=static int handle_futex_death(u32 __user *uaddr, struct task_struct *curr,
--
kernel/futex/core.c-686-         * this.
kernel/futex/core.c-687-         */
kernel/futex/core.c-688-        owner = uval & FUTEX_TID_MASK;
kernel/futex/core.c-689-
kernel/futex/core.c-690-        if (pending_op && !pi && !owner) {
kernel/futex/core.c:691:                futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY);
kernel/futex/core.c-692-                return 0;
kernel/futex/core.c-693-        }
kernel/futex/core.c-694-
kernel/futex/core.c-695-        if (owner != task_pid_vnr(curr))
kernel/futex/core.c-696-                return 0;
--
kernel/futex/core.c-739-        /*
kernel/futex/core.c-740-         * Wake robust non-PI futexes here. The wakeup of
kernel/futex/core.c-741-         * PI futexes happens in exit_pi_state():
kernel/futex/core.c-742-         */
kernel/futex/core.c-743-        if (!pi && (uval & FUTEX_WAITERS))
kernel/futex/core.c:744:                futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY);
kernel/futex/core.c-745-
kernel/futex/core.c-746-        return 0;
kernel/futex/core.c-747-}
kernel/futex/core.c-748-
kernel/futex/core.c-749-/*


Thanks,
Florian