From: Prarit Bhargava <prarit@redhat.com>
To: john stultz <johnstul@us.ibm.com>,
Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] [RFC] Potential fix for leapsecond caused futex related load spikes
Date: Sun, 01 Jul 2012 12:56:52 -0400 [thread overview]
Message-ID: <4FF08154.3050407@redhat.com> (raw)
In-Reply-To: <4FF06CAB.9020800@redhat.com>
On 07/01/2012 11:28 AM, Prarit Bhargava wrote:
> John,
>
> I was hit by the futex issue as well. I saw your patch and quickly did a test
> with top-of-tree + your patch using your reproducer. I end up with warnings
> from the smp_call_function code followed by all sorts of deadlocks, etc.
>
> I haven't had a chance to debug and will start doing so shortly ...
>
> intel-canoepass-02 login: [ 108.479555] Clock: inserting leap second 23:59:60 UTC
> [ 108.485199] ------------[ cut here ]------------
> [ 108.490368] WARNING: at kernel/smp.c:461 smp_call_function_many+0xbd/0x260()
> [ 108.498236] Hardware name: S2600CP
> [ 108.502060] Modules linked in: nfs nfs_acl auth_rpcgss fscache lockd sunrpc
> kvm_intel igb coretemp kvm ixgbe ptp pps_core ioatdma mdio tpm_tis crc32c_intel
> wmi joydev dca tpm lpc_ich ghash_clmulni_intel sb_edac mfd_core edac_core
> i2c_i801 microcode pcspkr tpm_bios hid_generic isci libsas scsi_transport_sas
> mgag200 i2c_algo_bit drm_kms_helper ttm drm i2c_core [last unloaded: scsi_wait_scan]
> [ 108.540561] Pid: 1328, comm: leaptest Not tainted 3.5.0-rc4+ #4
> [ 108.547169] Hypervisor: no hypervisor
> [ 108.551273] Call Trace:
> [ 108.554019] <IRQ> [<ffffffff8105814f>] warn_slowpath_common+0x7f/0xc0
> [ 108.561398] [<ffffffff810581aa>] warn_slowpath_null+0x1a/0x20
> [ 108.567911] [<ffffffff810b39bd>] smp_call_function_many+0xbd/0x260
> [ 108.574931] [<ffffffff8107e960>] ? hrtimer_wakeup+0x30/0x30
> [ 108.581242] [<ffffffff8107e960>] ? hrtimer_wakeup+0x30/0x30
> [ 108.587560] [<ffffffff810b3cb2>] smp_call_function+0x22/0x30
> [ 108.593982] [<ffffffff810b3d18>] on_each_cpu+0x28/0x70
> [ 108.599825] [<ffffffff8107ef7c>] clock_was_set+0x1c/0x30
John, the issue is that clock_was_set calls on_each_cpu() -- which cannot be
called from interrupt context as it calls smp_call_function_many().
I don't think you can call call_was_set() from update_wall_time() as
update_wall_time() is called in interrupt context.
Looking into it more ...
P.
next prev parent reply other threads:[~2012-07-01 16:56 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-01 15:28 [PATCH] [RFC] Potential fix for leapsecond caused futex related load spikes Prarit Bhargava
2012-07-01 16:56 ` Prarit Bhargava [this message]
2012-07-01 17:28 ` John Stultz
2012-07-02 10:16 ` Richard Cochran
2012-07-02 16:58 ` John Stultz
2012-07-02 20:08 ` Sytse Wielinga
2012-07-03 9:23 ` Richard Cochran
2012-07-03 12:05 ` Sytse Wielinga
2012-07-03 13:41 ` Richard Cochran
-- strict thread matches above, loose matches on Subject: below --
2012-07-01 9:36 John Stultz
2012-07-01 9:42 ` John Stultz
2012-07-01 12:00 ` Jan Ceuleers
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