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[192.184.162.253]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7488ffee527sm9352985b3a.19.2025.06.17.09.11.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 17 Jun 2025 09:11:08 -0700 (PDT) Date: Tue, 17 Jun 2025 09:11:06 -0700 From: Calvin Owens To: Sebastian Andrzej Siewior Cc: linux-kernel@vger.kernel.org, linux-tip-commits@vger.kernel.org, "Lai, Yi" , "Peter Zijlstra (Intel)" , x86@kernel.org Subject: Re: [tip: locking/urgent] futex: Allow to resize the private local hash Message-ID: References: <20250602110027.wfqbHgzb@linutronix.de> <174965275618.406.11364856155202390038.tip-bot2@tip-bot2> <20250617071628.lXtqjG7C@linutronix.de> <20250617095037.sOnrJlPX@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250617095037.sOnrJlPX@linutronix.de> On Tuesday 06/17 at 11:50 +0200, Sebastian Andrzej Siewior wrote: > On 2025-06-17 02:23:08 [-0700], Calvin Owens wrote: > > Ugh, I'm sorry, I was in too much of a hurry this morning... cargo is > > obviously not calling PR_FUTEX_HASH which is new in 6.16 :/ > No worries. > > > > This is with LTO enabled. > > > > Full lto with llvm-20.1.7. > > > … > > Nothing showed up in the logs but the RCU stalls on CPU16, always in > > queued_spin_lock_slowpath(). > > > > I'll run the build it was doing when it happened in a loop overnight and > > see if I can trigger it again. Actually got an oops this time: Oops: general protection fault, probably for non-canonical address 0xfdd92c90843cf111: 0000 [#1] SMP CPU: 3 UID: 1000 PID: 323127 Comm: cargo Not tainted 6.16.0-rc2-lto-00024-g9afe652958c3 #1 PREEMPT Hardware name: ASRock B850 Pro-A/B850 Pro-A, BIOS 3.11 11/12/2024 RIP: 0010:queued_spin_lock_slowpath+0x12a/0x1d0 Code: c8 c1 e8 10 66 87 47 02 66 85 c0 74 48 0f b7 c0 49 c7 c0 f8 ff ff ff 89 c6 c1 ee 02 83 e0 03 49 8b b4 f0 00 21 67 83 c1 e0 04 <48> 89 94 30 00 f1 4a 84 83 7a 08 00 75 10 0f 1f 84 00 00 00 00 00 RSP: 0018:ffffc9002c953d20 EFLAGS: 00010256 RAX: 0000000000000000 RBX: ffff88814e78be40 RCX: 0000000000100000 RDX: ffff88901fce5100 RSI: fdd92c90fff20011 RDI: ffff8881c2ae9384 RBP: 000000000000002b R08: fffffffffffffff8 R09: 00000000002ab900 R10: 000000000000b823 R11: 0000000000000c00 R12: ffff88814e78be40 R13: ffffc9002c953d48 R14: ffffc9002c953d48 R15: ffff8881c2ae9384 FS: 00007f086efb6600(0000) GS:ffff88909b836000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055ced9c42650 CR3: 000000034b88e000 CR4: 0000000000750ef0 PKRU: 55555554 Call Trace: futex_unqueue+0x2e/0x110 __futex_wait+0xc5/0x130 ? __futex_wake_mark+0xc0/0xc0 futex_wait+0xee/0x180 ? hrtimer_setup_sleeper_on_stack+0xe0/0xe0 do_futex+0x86/0x120 __se_sys_futex+0x16d/0x1e0 ? __x64_sys_write+0xba/0xc0 do_syscall_64+0x47/0x170 entry_SYSCALL_64_after_hwframe+0x4b/0x53 RIP: 0033:0x7f086e918779 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 4f 86 0d 00 f7 d8 64 89 01 48 RSP: 002b:00007ffc5815f678 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca RAX: ffffffffffffffda RBX: 00007f086e918760 RCX: 00007f086e918779 RDX: 000000000000002b RSI: 0000000000000089 RDI: 00005636f9fb60d0 RBP: 00007ffc5815f6d0 R08: 0000000000000000 R09: 00007ffcffffffff R10: 00007ffc5815f690 R11: 0000000000000246 R12: 000000001dcd6401 R13: 00007f086e833fd0 R14: 00005636f9fb60d0 R15: 000000000000002b ---[ end trace 0000000000000000 ]--- RIP: 0010:queued_spin_lock_slowpath+0x12a/0x1d0 Code: c8 c1 e8 10 66 87 47 02 66 85 c0 74 48 0f b7 c0 49 c7 c0 f8 ff ff ff 89 c6 c1 ee 02 83 e0 03 49 8b b4 f0 00 21 67 83 c1 e0 04 <48> 89 94 30 00 f1 4a 84 83 7a 08 00 75 10 0f 1f 84 00 00 00 00 00 RSP: 0018:ffffc9002c953d20 EFLAGS: 00010256 RAX: 0000000000000000 RBX: ffff88814e78be40 RCX: 0000000000100000 RDX: ffff88901fce5100 RSI: fdd92c90fff20011 RDI: ffff8881c2ae9384 RBP: 000000000000002b R08: fffffffffffffff8 R09: 00000000002ab900 R10: 000000000000b823 R11: 0000000000000c00 R12: ffff88814e78be40 R13: ffffc9002c953d48 R14: ffffc9002c953d48 R15: ffff8881c2ae9384 FS: 00007f086efb6600(0000) GS:ffff88909b836000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055ced9c42650 CR3: 000000034b88e000 CR4: 0000000000750ef0 PKRU: 55555554 Kernel panic - not syncing: Fatal exception Kernel Offset: disabled ---[ end Kernel panic - not syncing: Fatal exception ]--- This is a giant Yocto build, but the comm is always cargo, so hopefully I can run those bits in isolation and hit it more quickly. > Please check if you can reproduce it and if so if it also happens > without lto. > I have no idea why one spinlock_t remains locked. It is either locked or > some stray memory. > Oh. Lockdep adds quite some overhead but it should complain that a > spinlock_t is still locked while returning to userland. I'll report back when I've tried :) I'll also try some of the mm debug configs. Thanks, Calvin