linux-kernel - Re: [BUG] Why does mwait_idle_with_hints() call MWAIT with interrupts disabled ?

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Message-ID: <CAM3a_yr+KxisXDJcZChOtyYJYENFt7Uh1KPtZJ4rtgAF5vRqeQ@mail.gmail.com>
Date:	Sat, 9 Jul 2011 06:00:41 +0530
From:	Linux Smiths <linuxsmiths@...il.com>
To:	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [BUG] Why does mwait_idle_with_hints() call MWAIT with interrupts
 disabled ?

Venkatesh,
                 I see that you have introduced __sti_mwait(), so
maybe you can explain why we use __mwait() in mwait_idle_with_hints()
and __sti_mwait() in mwait_idle().

I know that even before your patch, mwait_idle_with_hints() used to
behave differently from mwait_idle(), in that it did not use to enable
interrupt before entering MWAIT sleep, but I'm hoping you can answer
this question for me.

Thanks,
Tomar

On Thu, Jul 7, 2011 at 6:10 AM, Tomar <tomar@...uxsmiths.com> wrote:
> Hi,
>   I'm seeing following crash consistently on my Dell R310 machine. The server
> is mostly idling while it crashes.
>
> I see that mwait_idle_with_hints() does not enable local interrupts before
> calling MWAIT. That does not appear right, as the only way now that this
> processor can be brought out of the sleep is by some other processor setting
> the need_resched flag that it is waiting on. In very low load situations this
> can take long and NMI lockup detection can kick in.
>
> mwait_idle() correctly reenables interrupts before the MWAIT call. Why is
> mwait_idle_with_hints() different, apart from the extra sleep state hints.
>
> I'v checked the latest kernel sources and this part remains the same.
>
> This code is pretty old, so I wonder if other people are also seeing this
> problem.
>
> Thanks,
> Tomar
>
>
> Following is the crash backtrace.
>
>
> [ 4997.164914] BUG: NMI Watchdog detected LOCKUP on CPU1, ip
> ffffffff8101a399, registers:
> [ 4997.165025] CPU 1
> [ 4997.165121] Modules linked in: netconsole configfs xfrm_user
> xfrm4_tunnel tunnel4 ipcomp xfrm_ipcomp esp4 ah4 deflate zlib_deflate
> ctr twofish twofish_common camellia serpent blowfish cast5 des_generic
> cryptd aes_x86_64 aes_generic xcbc rmd160 sha256_generic sha1_generic
> crypto_null af_key bonding xfs exportfs joydev usbhid hid igb dca
> e1000e sctp crc32c libcrc32c dell_wmi 8021q dcdbas garp stp
> power_meter tcp_westwood tcp_veno tcp_vegas tcp_hybla bnx2 lp parport
> [ 4997.167856] Pid: 0, comm: swapper Not tainted 2.6.32-27-server-test
> #0test2 PowerEdge R310
> [ 4997.167968] RIP: 0010:[<ffffffff8101a399>]  [<ffffffff8101a399>]
> mwait_idle_with_hints+0x99/0xf0
> [ 4997.168109] RSP: 0018:ffff88013baffe48  EFLAGS: 00000046
> [ 4997.168217] RAX: 0000000000000020 RBX: 0000000000000020 RCX: 0000000000000001
> [ 4997.168290] RDX: 0000000000000000 RSI: ffff88013bafffd8 RDI: 0000000000000000
> [ 4997.168363] RBP: ffff88013baffe68 R08: 0000000000000000 R09: 0000000000000060
> [ 4997.168435] R10: 0000048d19b9c2bd R11: 0000000000000000 R12: 0000000000000001
> [ 4997.168508] R13: 0000000000000003 R14: 0000000000000000 R15: 0000000000000000
> [ 4997.168581] FS:  0000000000000000(0000) GS:ffff88000d620000(0000)
> knlGS:0000000000000000
> [ 4997.168724] CS:  0010 DS: 0018 ES: 0018 CR0: 000000008005003b
> [ 4997.168795] CR2: 00007f03388da000 CR3: 0000000001001000 CR4: 00000000000006e0
> [ 4997.168867] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [ 4997.168940] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> [ 4997.169013] Process swapper (pid: 0, threadinfo ffff88013bafe000,
> task ffff88013baf44a0)
> [ 4997.169153] Stack:
> [ 4997.169216]  ffff880139e09530 ffff880139e09000 122be5d25988d251
> 0000000000000000
> [ 4997.169427] <0> ffff88013baffe78 ffffffff8102c9c2 ffff88013baffe88
> ffffffff8130e6e6
> [ 4997.169741] <0> ffff88013baffee8 ffffffff8130ea04 ffff88013baffea8
> ffffffff81088718
> [ 4997.170115] Call Trace:
> [ 4997.170182]  [<ffffffff8102c9c2>] acpi_processor_ffh_cstate_enter+0x32/0x40
> [ 4997.170310]  [<ffffffff8130e6e6>] acpi_idle_do_entry+0x15/0x67
> [ 4997.170382]  [<ffffffff8130ea04>] acpi_idle_enter_bm+0x20b/0x2c8
> [ 4997.170456]  [<ffffffff81088718>] ? hrtimer_start+0x18/0x20
> [ 4997.170529]  [<ffffffff81551f96>] ? notifier_call_chain+0x16/0x80
> [ 4997.170602]  [<ffffffff814437dd>] ? menu_select+0x10d/0x2a0
> [ 4997.170673]  [<ffffffff81442717>] cpuidle_idle_call+0xa7/0x140
> [ 4997.170746]  [<ffffffff81010e63>] cpu_idle+0xb3/0x110
> [ 4997.170817]  [<ffffffff81547086>] start_secondary+0xa8/0xaa
> [ 4997.170887] Code: 8b 34 25 c8 cb 00 00 48 89 d1 48 8d 86 38 e0 ff
> ff 0f 01 c8 0f ae f0 48 8b 86 38 e0 ff ff a8 08 75 09 48 89 d8 4c 89
> e1 0f 01 c9 <48> 8b 1c 24 4c 8b 64 24 08 4c 8b 6c 24 10 4c 8b 74 24 18
> c9 c3
>
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