From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from outpost1.zedat.fu-berlin.de (outpost1.zedat.fu-berlin.de [130.133.4.66]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 936E628B41E; Fri, 8 Aug 2025 22:37:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=130.133.4.66 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754692643; cv=none; b=KpZqffM5V3M6tU5x1d5SGmW69VIb518CqjrN+fLS4NjkYhH7gwAz+//f13dF7W7MwY8WDJuLuHVYmmEdnvn8EfPL9Xjv2pEuu/9kuQWqKXhocgCHLy66QsBQ2gXDB3r0zvg5D8043Y9tRgsA36lHbybbfZdcJtAb//077C6F6O4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754692643; c=relaxed/simple; bh=JHVmu2n/nTTH6LX4nabX1OA53QT7DxKgSG23yl+OzXY=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=II5rlI3pZZl8Iw1VIFIzDcfV6sTNa4IK56DRDeenRSqGqR4d4JI0Un1wHylIyDwEMlkITLgX7KvLFRI5QU69R6HEjvOheTeSFpa+AIozNZ+cb7FMfRisfs0Booac1cNz4rB37EORfDsJNW8CPGJrKFL/hFfFVvCsSL4AWNNH6Xk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=physik.fu-berlin.de; spf=pass smtp.mailfrom=zedat.fu-berlin.de; dkim=pass (2048-bit key) header.d=fu-berlin.de header.i=@fu-berlin.de header.b=mkjdQ0A/; arc=none smtp.client-ip=130.133.4.66 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=physik.fu-berlin.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zedat.fu-berlin.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=fu-berlin.de header.i=@fu-berlin.de header.b="mkjdQ0A/" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=fu-berlin.de; s=fub01; h=MIME-Version:Content-Transfer-Encoding: Content-Type:References:In-Reply-To:Date:Cc:To:From:Subject:Message-ID:From: Reply-To:Subject:Date:Message-ID:To:Cc:MIME-Version:Content-Type: Content-Transfer-Encoding:Content-ID:Content-Description:In-Reply-To: References; bh=lusU9fDt0+doSISdjWA/f49G8mbzLTv949xNyjBeF9A=; t=1754692640; x=1755297440; b=mkjdQ0A/00dhYMnzcrOQZ/ZouwaVyNfZ3PWFtwtxaxdlhB/tpMNh23jkgxlX3 V1J6QlQ9Scmn3tGBVi5RhzKG1kPUSjjS5NrmLa6iunwC3SjuID6zZMqLnaZD+eKZLOgBl8yitMbpQ CaIiAA885p1xS7N2jMUytJAz6yIeAOuTT0O2sx0VwNrtt1DWX/LGAiz+CUcJSJ03LNgY11pUqKvNN 5knkgV0PcWpjfQn4g8jZSiq81iYlVbhTAabnIa7RN2CVwiKfV2JskKn2f0UvSZWv7XzUq1w/mj35b BR2UVsk2YQ5SLFgR9bOGk9QTo0UR+h96BKMQz9dZ1VTxd1qkog==; Received: from inpost2.zedat.fu-berlin.de ([130.133.4.69]) by outpost.zedat.fu-berlin.de (Exim 4.98) with esmtps (TLS1.3) tls TLS_AES_256_GCM_SHA384 (envelope-from ) id 1ukVi7-00000003f3G-2ulW; Sat, 09 Aug 2025 00:37:15 +0200 Received: from dynamic-002-242-002-090.2.242.pool.telefonica.de ([2.242.2.90] helo=[192.168.178.50]) by inpost2.zedat.fu-berlin.de (Exim 4.98) with esmtpsa (TLS1.3) tls TLS_AES_256_GCM_SHA384 (envelope-from ) id 1ukVi7-00000001Le7-1qeS; Sat, 09 Aug 2025 00:37:15 +0200 Message-ID: <38f4469f48e6d36fa92b445c8ecef7a440be43e6.camel@physik.fu-berlin.de> Subject: Re: [PATCH] sparc64: fix hugetlb for sun4u From: John Paul Adrian Glaubitz To: Anthony Yznaga , sparclinux@vger.kernel.org, davem@davemloft.net, andreas@gaisler.com Cc: linux-kernel@vger.kernel.org, agordeev@linux.ibm.com, will@kernel.org, ryan.roberts@arm.com, david@redhat.com, osalvador@suse.de Date: Sat, 09 Aug 2025 00:37:14 +0200 In-Reply-To: <7e1e9aa5-0529-4fb5-84fb-557b5cc1cd50@oracle.com> References: <20250716012446.10357-1-anthony.yznaga@oracle.com> <35f5ec4eda8a7dbeeb7df9ec0be5c0b062c509f7.camel@physik.fu-berlin.de> <7e1e9aa5-0529-4fb5-84fb-557b5cc1cd50@oracle.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Original-Sender: glaubitz@physik.fu-berlin.de X-ZEDAT-Hint: PO Hi Anthony, On Fri, 2025-08-08 at 15:15 -0700, Anthony Yznaga wrote: > > So, I have to admit that I'm not an expert on Linux kernel memory manag= ement and > > don't exactly know what the difference between HugeTLB and Transparent = Huge Pages > > is. Could someone enlighten me? >=20 > They both use use huge pages to reduce the number of TLB misses. HugeTLB= =20 > has to be configured and requires changes to an application to=20 > explicitly use it. THP works in a more automated fashion where the=20 > kernel manages when and where to use huge pages without requiring=20 > changes to the application. Thanks for the explanation! I had actually researched the difference in the= mean time because I was curious about it ;-). > >=20 > > The reason I am asking is because while this patch seems to fix HugeTLB= support, > > we're still seeing TLB-related crashes on sun4u which are triggered whe= n both > > CONFIG_TRANSPARENT_HUGEPAGE and CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS are = set. > >=20 > > I previously thought that HugeTLB and THP are the same, but it seems li= ke that's > > not the case. >=20 > Yes, my patch fixes HugeTLB only, and has no bearing on THP. >=20 > >=20 > > Enabling both these options leads to the following backtrace during boo= t: > >=20 > > [ 29.858572] rcu: INFO: rcu_sched detected stalls on CPUs/tasks: > > [ 29.858580] rcu: (detected by 0, t=3D2109 jiffies, g=3D-1155, q= =3D3 ncpus=3D1) > > [ 29.858586] rcu: All QSes seen, last rcu_sched kthread activity 2109= (4294939474-4294937365), jiffies_till_next_fqs=3D1, root ->qsmask 0x0 > > [ 29.858595] rcu: rcu_sched kthread starved for 2109 jiffies! g-1155 = f0x2 RCU_GP_WAIT_FQS(5) ->state=3D0x0 ->cpu=3D0 > > [ 29.858603] rcu: Unless rcu_sched kthread gets sufficient CPU ti= me, OOM is now expected behavior. > > [ 29.858606] rcu: RCU grace-period kthread stack dump: > > [ 29.858609] task:rcu_sched state:R running task stack:0 = pid:15 tgid:15 ppid:2 task_flags:0x208040 flags:0x07000000 > > [ 29.858626] Call Trace: > > [ 29.858629] [<0000000000c0a234>] schedule+0x14/0x160 > > [ 29.858646] [<0000000000c11194>] schedule_timeout+0x54/0xe0 > > [ 29.858657] [<00000000004fbd40>] rcu_gp_fqs_loop+0x140/0x6c0 > > [ 29.858669] [<000000000050003c>] rcu_gp_kthread+0x23c/0x2a0 > > [ 29.858678] [<000000000049b788>] kthread+0xe8/0x120 > > [ 29.858688] [<00000000004060c8>] ret_from_fork+0x1c/0x2c > > [ 29.858700] [<0000000000000000>] 0x0 > > [ 29.858705] rcu: Stack dump where RCU GP kthread last ran: > > [ 29.858710] CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.16.0+= #32 VOLUNTARY > > [ 29.858719] TSTATE: 0000004411001603 TPC: 00000000004db400 TNPC: 000= 00000004db404 Y: 0000137d Not tainted > > [ 29.858725] TPC: > > [ 29.858738] g0: 00000000004db400 g1: 0000000000000000 g2: 0000000000= 000000 g3: 00000000017fd000 > > [ 29.858743] g4: fff0000000180000 g5: fff000023d194000 g6: fff0000000= 158000 g7: 000000000000000e > > [ 29.858748] o0: 00000000017fd1e0 o1: 0000000000000000 o2: 0000000000= 000000 o3: 00000000017fc5d0 > > [ 29.858752] o4: 0000000000000000 o5: 000000000185d7e8 sp: fff0000000= 15a901 ret_pc: 00000000004db3f0 > > [ 29.858757] RPC: > > [ 29.858764] l0: 00000000017fc5d0 l1: 0000000000000000 l2: 0000000000= 000000 l3: 000000000143b538 > > [ 29.858769] l4: 0000000000000000 l5: 0000000000000001 l6: 0000000001= 5c20b0 l7: 0000000001536308 > > [ 29.858773] i0: 0000000000000000 i1: fff000000015b2b8 i2: fff0000000= 15b2b3 i3: 0000000000000000 > > [ 29.858778] i4: 00000000017fd1e0 i5: 0000000000000001 i6: fff0000000= 15aa01 i7: 00000000004db5e8 > > [ 29.858782] I7: > > [ 29.858790] Call Trace: > > [ 29.858793] [<00000000004db5e8>] console_unlock+0x88/0x120 > > [ 29.858801] [<00000000004dc128>] vprintk_emit+0x1e8/0x280 > > [ 29.858809] [<000000000042a34c>] _printk+0x20/0x30 > > [ 29.858819] [<00000000004dc66c>] register_console+0x34c/0x580 > > [ 29.858828] [<0000000000920358>] serial_core_register_port+0x898/0x8= c0 > > [ 29.858835] [<000000000092555c>] su_probe+0x15c/0x3e0 > > [ 29.858844] [<0000000000936d88>] platform_probe+0x28/0x80 > > [ 29.858851] [<0000000000934338>] really_probe+0xb8/0x340 > > [ 29.858863] [<0000000000934764>] driver_probe_device+0x24/0x120 > > [ 29.858872] [<0000000000934a0c>] __driver_attach+0x8c/0x1a0 > > [ 29.858879] [<000000000093232c>] bus_for_each_dev+0x4c/0xa0 > > [ 29.858887] [<0000000000933668>] bus_add_driver+0x148/0x220 > > [ 29.858894] [<0000000000935634>] driver_register+0x74/0x120 > > [ 29.858903] [<0000000001635e3c>] sunsu_init+0x180/0x1dc > > [ 29.858915] [<00000000004347b0>] do_one_initcall+0x30/0x240 > > [ 29.858924] [<000000000160d014>] kernel_init_freeable+0x244/0x2b8 > >=20 > > Running the apt package manager results in a minute-long hang and this = backtrace: > >=20 > > [ 112.800879] systemd-journald[154]: Time jumped backwards, rotating. > > [ 123.148552] kernel BUG at fs/ext4/inode.c:1174! > > [ 123.208162] \|/ ____ \|/ > > [ 123.208162] "@'/ .. \`@" > > [ 123.208162] /_| \__/ |_\ > > [ 123.208162] \__U_/ > > [ 123.401513] apt(881): Kernel bad sw trap 5 [#1] > > [ 123.461051] CPU: 0 UID: 0 PID: 881 Comm: apt Not tainted 6.16.0+ #32= VOLUNTARY > > [ 123.557129] TSTATE: 0000004411001603 TPC: 000000000075eda8 TNPC: 000= 000000075edac Y: 00000000 Not tainted > > [ 123.686379] TPC: > > [ 123.752813] g0: 0000000000000000 g1: 0000000000000001 g2: 0000000000= 000000 g3: 0000000000000000 > > [ 123.867186] g4: fff0000007eb8140 g5: fff000023d194000 g6: fff000000a= 130000 g7: 0000000000000001 > > [ 123.981565] o0: 0000000000000023 o1: 0000000000d74b28 o2: 0000000000= 000496 o3: 0000000000101cca > > [ 124.095948] o4: 0000000001568800 o5: 0000000000000000 sp: fff000000a= 133161 ret_pc: 000000000075eda0 > > [ 124.214890] RPC: > > [ 124.281219] l0: fff00000029ce828 l1: 0000000000113cca l2: fff0000002= 9ce6c0 l3: 0000000000001000 > > [ 124.395608] l4: 0000000000000002 l5: 0000000000080000 l6: 0000000000= 012000 l7: 0000000000000001 > > [ 124.509978] i0: 0000000000000000 i1: 000c0000003bfa00 i2: 0000000000= 001fc0 i3: 0000000000680000 > > [ 124.624351] i4: 0000000000000000 i5: 0000000000000000 i6: fff000000a= 133251 i7: 0000000000762518 > > [ 124.738729] I7: > > [ 124.800487] Call Trace: > > [ 124.832506] [<0000000000762518>] ext4_da_write_begin+0x158/0x300 > > [ 124.911429] [<00000000005b84ac>] generic_perform_write+0x8c/0x240 > > [ 124.991491] [<000000000074ae30>] ext4_buffered_write_iter+0x50/0x120 > > [ 125.074997] [<0000000000695420>] vfs_write+0x2a0/0x400 > > [ 125.142468] [<00000000006956c4>] ksys_write+0x44/0xe0 > > [ 125.208805] [<0000000000406274>] linux_sparc_syscall+0x34/0x44 > > [ 125.285437] Disabling lock debugging due to kernel taint > > [ 125.355205] Caller[0000000000762518]: ext4_da_write_begin+0x158/0x30= 0 > > [ 125.439843] Caller[00000000005b84ac]: generic_perform_write+0x8c/0x2= 40 > > [ 125.525624] Caller[000000000074ae30]: ext4_buffered_write_iter+0x50/= 0x120 > > [ 125.614836] Caller[0000000000695420]: vfs_write+0x2a0/0x400 > > [ 125.688035] Caller[00000000006956c4]: ksys_write+0x44/0xe0 > > [ 125.760093] Caller[0000000000406274]: linux_sparc_syscall+0x34/0x44 > > [ 125.842442] Caller[0000000000000000]: 0x0 > > [ 125.895052] Instruction DUMP: > > [ 125.895055] 110035d2 > > [ 125.933938] 7ff35910 > > [ 125.964823] 90122328 > > [ 125.995700] <91d02005> > > [ 126.026582] 80a06000 > > [ 126.057466] 02480010 > > [ 126.088347] d45fa7cf > > [ 126.119224] d85fa7cf > > [ 126.150125] 9736a000 > > [ 126.181088] > >=20 > > After applying this patch to fix HugeTLB support on sun4u, the backtrac= e during boot changes to: > >=20 > > [ 29.860234] rcu: INFO: rcu_sched detected stalls on CPUs/tasks: > > [ 29.860241] rcu: (detected by 0, t=3D2109 jiffies, g=3D-1151, q= =3D3 ncpus=3D1) > > [ 29.860247] rcu: All QSes seen, last rcu_sched kthread activity 2109= (4294939474-4294937365), jiffies_till_next_fqs=3D1, root ->qsmask 0x0 > > [ 29.860256] rcu: rcu_sched kthread starved for 2109 jiffies! g-1151 = f0x2 RCU_GP_WAIT_FQS(5) ->state=3D0x0 ->cpu=3D0 > > [ 29.860263] rcu: Unless rcu_sched kthread gets sufficient CPU ti= me, OOM is now expected behavior. > > [ 29.860266] rcu: RCU grace-period kthread stack dump: > > [ 29.860269] task:rcu_sched state:R running task stack:0 = pid:15 tgid:15 ppid:2 task_flags:0x208040 flags:0x07000000 > > [ 29.860285] Call Trace: > > [ 29.860288] [<0000000000c0a2f4>] schedule+0x14/0x160 > > [ 29.860305] [<0000000000c11254>] schedule_timeout+0x54/0xe0 > > [ 29.860317] [<00000000004fbe00>] rcu_gp_fqs_loop+0x140/0x6c0 > > [ 29.860329] [<00000000005000fc>] rcu_gp_kthread+0x23c/0x2a0 > > [ 29.860338] [<000000000049b848>] kthread+0xe8/0x120 > > [ 29.860347] [<00000000004060c8>] ret_from_fork+0x1c/0x2c > > [ 29.860359] [<0000000000000000>] 0x0 > > [ 29.860364] rcu: Stack dump where RCU GP kthread last ran: > > [ 29.860368] CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.16.0+= #33 VOLUNTARY > > [ 29.860378] TSTATE: 0000004411001603 TPC: 00000000004db4c0 TNPC: 000= 00000004db4c4 Y: 00001390 Not tainted > > [ 29.860383] TPC: > > [ 29.860397] g0: 00000000004db4c0 g1: 0000000000000000 g2: 0000000000= 000000 g3: 00000000017fd000 > > [ 29.860401] g4: fff0000000180000 g5: fff000023d194000 g6: fff0000000= 158000 g7: 000000000000000e > > [ 29.860406] o0: 00000000017fd1e0 o1: 0000000000000000 o2: 0000000000= 000000 o3: 00000000017fc5d0 > > [ 29.860411] o4: 0000000000000000 o5: 000000000185d7e8 sp: fff0000000= 15a901 ret_pc: 00000000004db4b0 > > [ 29.860415] RPC: > > [ 29.860423] l0: 00000000017fc5d0 l1: 0000000000000000 l2: 0000000000= 000000 l3: 000000000143b538 > > [ 29.860427] l4: 0000000000000000 l5: 0000000000000001 l6: 0000000001= 5c20b0 l7: 0000000001536308 > > [ 29.860432] i0: 0000000000000000 i1: fff000000015b2b8 i2: fff0000000= 15b2b3 i3: 0000000000000000 > > [ 29.860436] i4: 00000000017fd1e0 i5: 0000000000000001 i6: fff0000000= 15aa01 i7: 00000000004db6a8 > > [ 29.860441] I7: > > [ 29.860449] Call Trace: > > [ 29.860451] [<00000000004db6a8>] console_unlock+0x88/0x120 > > [ 29.860459] [<00000000004dc1e8>] vprintk_emit+0x1e8/0x280 > > [ 29.860467] [<000000000042a34c>] _printk+0x20/0x30 > > [ 29.860477] [<00000000004dc72c>] register_console+0x34c/0x580 > > [ 29.860485] [<0000000000920418>] serial_core_register_port+0x898/0x8= c0 > > [ 29.860493] [<000000000092561c>] su_probe+0x15c/0x3e0 > > [ 29.860502] [<0000000000936e48>] platform_probe+0x28/0x80 > > [ 29.860509] [<00000000009343f8>] really_probe+0xb8/0x340 > > [ 29.860521] [<0000000000934824>] driver_probe_device+0x24/0x120 > > [ 29.860529] [<0000000000934acc>] __driver_attach+0x8c/0x1a0 > > [ 29.860537] [<00000000009323ec>] bus_for_each_dev+0x4c/0xa0 > > [ 29.860544] [<0000000000933728>] bus_add_driver+0x148/0x220 > > [ 29.860552] [<00000000009356f4>] driver_register+0x74/0x120 > > [ 29.860560] [<0000000001635e3c>] sunsu_init+0x180/0x1dc > > [ 29.860572] [<00000000004347b0>] do_one_initcall+0x30/0x240 > > [ 29.860581] [<000000000160d014>] kernel_init_freeable+0x244/0x2b > >=20 > > while the backtrace produced when apt hangs is: > > =20 > > [ 337.599490] ------------[ cut here ]------------ > > [ 337.660412] WARNING: CPU: 0 PID: 895 at fs/ext4/extents_status.c:298= __es_find_extent_range+0x128/0x140 > > [ 337.784523] Modules linked in: sg sr_mod cdrom sym53c8xx tg3 libphy = mdio_bus > > [ 337.877302] CPU: 0 UID: 0 PID: 895 Comm: apt Not tainted 6.16.0+ #33= VOLUNTARY > > [ 337.877314] Call Trace: > > [ 337.877316] [<000000000047286c>] __warn+0x10c/0x120 > > [ 337.877326] [<0000000000472910>] warn_slowpath_fmt+0x90/0x120 > > [ 337.877332] [<0000000000748988>] __es_find_extent_range+0x128/0x140 > > [ 337.877341] [<00000000007490f0>] ext4_es_find_extent_range+0x50/0x10= 0 > > [ 337.877348] [<0000000000742a1c>] ext4_ext_map_blocks+0x7fc/0x22a0 > > [ 337.877355] [<00000000007578d0>] ext4_map_query_blocks+0x30/0x2a0 > > [ 337.877366] [<00000000007596a0>] ext4_da_get_block_prep+0x380/0x640 > > [ 337.877375] [<000000000075ecf4>] ext4_block_write_begin+0x294/0x480 > > [ 337.877382] [<00000000007625d8>] ext4_da_write_begin+0x158/0x300 > > [ 337.877389] [<00000000005b856c>] generic_perform_write+0x8c/0x240 > > [ 337.877399] [<000000000074aef0>] ext4_buffered_write_iter+0x50/0x120 > > [ 337.877406] [<00000000006954e0>] vfs_write+0x2a0/0x400 > > [ 337.877415] [<0000000000695784>] ksys_write+0x44/0xe0 > > [ 337.877421] [<0000000000406274>] linux_sparc_syscall+0x34/0x44 > > [ 337.877433] ---[ end trace 0000000000000000 ]--- > > [ 339.153555] ------------[ cut here ]------------ > > [ 339.214459] WARNING: CPU: 0 PID: 895 at fs/ext4/extents_status.c:298= __es_find_extent_range+0x128/0x140 > > [ 339.338108] Modules linked in: sg sr_mod cdrom sym53c8xx tg3 libphy = mdio_bus > > [ 339.430869] CPU: 0 UID: 0 PID: 895 Comm: apt Tainted: G W = 6.16.0+ #33 VOLUNTARY > > [ 339.430880] Tainted: [W]=3DWARN > > [ 339.430883] Call Trace: > > [ 339.430886] [<000000000047286c>] __warn+0x10c/0x120 > > [ 339.430894] [<0000000000472910>] warn_slowpath_fmt+0x90/0x120 > > [ 339.430900] [<0000000000748988>] __es_find_extent_range+0x128/0x140 > > [ 339.430907] [<00000000007490f0>] ext4_es_find_extent_range+0x50/0x10= 0 > > [ 339.430915] [<0000000000742a1c>] ext4_ext_map_blocks+0x7fc/0x22a0 > > [ 339.430921] [<00000000007578d0>] ext4_map_query_blocks+0x30/0x2a0 > > [ 339.430931] [<00000000007597d4>] ext4_da_get_block_prep+0x4b4/0x640 > > [ 339.430940] [<000000000075ecf4>] ext4_block_write_begin+0x294/0x480 > > [ 339.430948] [<00000000007625d8>] ext4_da_write_begin+0x158/0x300 > > [ 339.430954] [<00000000005b856c>] generic_perform_write+0x8c/0x240 > > [ 339.430964] [<000000000074aef0>] ext4_buffered_write_iter+0x50/0x120 > > [ 339.430971] [<00000000006954e0>] vfs_write+0x2a0/0x400 > > [ 339.430979] [<0000000000695784>] ksys_write+0x44/0xe0 > > [ 339.430985] [<0000000000406274>] linux_sparc_syscall+0x34/0x44 > > [ 339.430996] ---[ end trace 0000000000000000 ]--- > >=20 > > So, I guess while your patch may fix HugeTLB support, there is still a = bug on sun4u with THP > > which needs to be addressed. >=20 > Maybe try enabling CONFIG_DEBUG_VM_IRQSOFF, CONFIG_DEBUG_VM, and perhaps= =20 > CONFIG_DEBUG_VM_PGFLAGS. That might help detect a problem closer to the= =20 > source. You can also try adding transparent_hugepage=3Dnever to the kerne= l=20 > boot line to see if compiling in THP support but not using it is okay. OK, I will try that. But not today anymore. It's half past midnight now her= e in Germany and I was debugging this issue almost all day long. I'm glad to have finall= y been able to track this down to THP support being enabled. Maybe you can try whether you can reproduce this in QEMU as well. Adrian --=20 .''`. John Paul Adrian Glaubitz : :' : Debian Developer `. `' Physicist `- GPG: 62FF 8A75 84E0 2956 9546 0006 7426 3B37 F5B5 F913