kernel/linux.git, branch v4.19.148

Linux 4.19.148

2020-09-26T16:01:33+00:00

Tested-by: Jon Hunter Tested-by: Shuah Khan Tested-by: Linux Kernel Functional Testing Tested-by: Guenter Roeck Signed-off-by: Greg Kroah-Hartman Link: https://lore.kernel.org/r/20200925124720.972208530@linuxfoundation.org Signed-off-by: Greg Kroah-Hartman

serial: 8250: Avoid error message on reprobe

2020-09-26T16:01:32+00:00

commit e0a851fe6b9b619527bd928aa93caaddd003f70c upstream. If the call to uart_add_one_port() in serial8250_register_8250_port() fails, a half-initialized entry in the serial_8250ports[] array is left behind. A subsequent reprobe of the same serial port causes that entry to be reused. Because uart->port.dev is set, uart_remove_one_port() is called for the half-initialized entry and bails out with an error message: bcm2835-aux-uart 3f215040.serial: Removing wrong port: (null) != (ptrval) The same happens on failure of mctrl_gpio_init() since commit 4a96895f74c9 ("tty/serial/8250: use mctrl_gpio helpers"). Fix by zeroing the uart->port.dev pointer in the probe error path. The bug was introduced in v2.6.10 by historical commit befff6f5bf5f ("[SERIAL] Add new port registration/unregistration functions."): https://git.kernel.org/tglx/history/c/befff6f5bf5f The commit added an unconditional call to uart_remove_one_port() in serial8250_register_port(). In v3.7, commit 835d844d1a28 ("8250_pnp: do pnp probe before legacy probe") made that call conditional on uart->port.dev which allows me to fix the issue by zeroing that pointer in the error path. Thus, the present commit will fix the problem as far back as v3.7 whereas still older versions need to also cherry-pick 835d844d1a28. Fixes: 835d844d1a28 ("8250_pnp: do pnp probe before legacy probe") Signed-off-by: Lukas Wunner Cc: stable@vger.kernel.org # v2.6.10 Cc: stable@vger.kernel.org # v2.6.10: 835d844d1a28: 8250_pnp: do pnp probe before legacy Reviewed-by: Andy Shevchenko Link: https://lore.kernel.org/r/b4a072013ee1a1d13ee06b4325afb19bda57ca1b.1589285873.git.lukas@wunner.de [iwamatsu: Backported to 4.14, 4.19: adjust context] Signed-off-by: Nobuhiro Iwamatsu (CIP) Signed-off-by: Greg Kroah-Hartman

tcp_bbr: adapt cwnd based on ack aggregation estimation

2020-09-26T16:01:32+00:00

commit 78dc70ebaa38aa303274e333be6c98eef87619e2 upstream. Aggregation effects are extremely common with wifi, cellular, and cable modem link technologies, ACK decimation in middleboxes, and LRO and GRO in receiving hosts. The aggregation can happen in either direction, data or ACKs, but in either case the aggregation effect is visible to the sender in the ACK stream. Previously BBR's sending was often limited by cwnd under severe ACK aggregation/decimation because BBR sized the cwnd at 2*BDP. If packets were acked in bursts after long delays (e.g. one ACK acking 5*BDP after 5*RTT), BBR's sending was halted after sending 2*BDP over 2*RTT, leaving the bottleneck idle for potentially long periods. Note that loss-based congestion control does not have this issue because when facing aggregation it continues increasing cwnd after bursts of ACKs, growing cwnd until the buffer is full. To achieve good throughput in the presence of aggregation effects, this algorithm allows the BBR sender to put extra data in flight to keep the bottleneck utilized during silences in the ACK stream that it has evidence to suggest were caused by aggregation. A summary of the algorithm: when a burst of packets are acked by a stretched ACK or a burst of ACKs or both, BBR first estimates the expected amount of data that should have been acked, based on its estimated bandwidth. Then the surplus ("extra_acked") is recorded in a windowed-max filter to estimate the recent level of observed ACK aggregation. Then cwnd is increased by the ACK aggregation estimate. The larger cwnd avoids BBR being cwnd-limited in the face of ACK silences that recent history suggests were caused by aggregation. As a sanity check, the ACK aggregation degree is upper-bounded by the cwnd (at the time of measurement) and a global max of BW * 100ms. The algorithm is further described by the following presentation: https://datatracker.ietf.org/meeting/101/materials/slides-101-iccrg-an-update-on-bbr-work-at-google-00 In our internal testing, we observed a significant increase in BBR throughput (measured using netperf), in a basic wifi setup. - Host1 (sender on ethernet) -> AP -> Host2 (receiver on wifi) - 2.4 GHz -> BBR before: ~73 Mbps; BBR after: ~102 Mbps; CUBIC: ~100 Mbps - 5.0 GHz -> BBR before: ~362 Mbps; BBR after: ~593 Mbps; CUBIC: ~601 Mbps Also, this code is running globally on YouTube TCP connections and produced significant bandwidth increases for YouTube traffic. This is based on Ian Swett's max_ack_height_ algorithm from the QUIC BBR implementation. Signed-off-by: Priyaranjan Jha Signed-off-by: Neal Cardwell Signed-off-by: Yuchung Cheng Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman

tcp_bbr: refactor bbr_target_cwnd() for general inflight provisioning

2020-09-26T16:01:32+00:00

commit 232aa8ec3ed979d4716891540c03a806ecab0c37 upstream. Because bbr_target_cwnd() is really a general-purpose BBR helper for computing some volume of inflight data as a function of the estimated BDP, refactor it into following helper functions: - bbr_bdp() - bbr_quantization_budget() - bbr_inflight() Signed-off-by: Priyaranjan Jha Signed-off-by: Neal Cardwell Signed-off-by: Yuchung Cheng Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman

mm: memcg: fix memcg reclaim soft lockup

2020-09-26T16:01:32+00:00

commit e3336cab2579012b1e72b5265adf98e2d6e244ad upstream. We've met softlockup with "CONFIG_PREEMPT_NONE=y", when the target memcg doesn't have any reclaimable memory. It can be easily reproduced as below: watchdog: BUG: soft lockup - CPU#0 stuck for 111s![memcg_test:2204] CPU: 0 PID: 2204 Comm: memcg_test Not tainted 5.9.0-rc2+ #12 Call Trace: shrink_lruvec+0x49f/0x640 shrink_node+0x2a6/0x6f0 do_try_to_free_pages+0xe9/0x3e0 try_to_free_mem_cgroup_pages+0xef/0x1f0 try_charge+0x2c1/0x750 mem_cgroup_charge+0xd7/0x240 __add_to_page_cache_locked+0x2fd/0x370 add_to_page_cache_lru+0x4a/0xc0 pagecache_get_page+0x10b/0x2f0 filemap_fault+0x661/0xad0 ext4_filemap_fault+0x2c/0x40 __do_fault+0x4d/0xf9 handle_mm_fault+0x1080/0x1790 It only happens on our 1-vcpu instances, because there's no chance for oom reaper to run to reclaim the to-be-killed process. Add a cond_resched() at the upper shrink_node_memcgs() to solve this issue, this will mean that we will get a scheduling point for each memcg in the reclaimed hierarchy without any dependency on the reclaimable memory in that memcg thus making it more predictable. Suggested-by: Michal Hocko Signed-off-by: Xunlei Pang Signed-off-by: Andrew Morton Acked-by: Chris Down Acked-by: Michal Hocko Acked-by: Johannes Weiner Link: http://lkml.kernel.org/r/1598495549-67324-1-git-send-email-xlpang@linux.alibaba.com Signed-off-by: Linus Torvalds Signed-off-by: Julius Hemanth Pitti Signed-off-by: Greg Kroah-Hartman

kbuild: support LLVM=1 to switch the default tools to Clang/LLVM

2020-09-26T16:01:32+00:00

commit a0d1c951ef08ed24f35129267e3595d86f57f5d3 upstream. As Documentation/kbuild/llvm.rst implies, building the kernel with a full set of LLVM tools gets very verbose and unwieldy. Provide a single switch LLVM=1 to use Clang and LLVM tools instead of GCC and Binutils. You can pass it from the command line or as an environment variable. Please note LLVM=1 does not turn on the integrated assembler. You need to pass LLVM_IAS=1 to use it. When the upstream kernel is ready for the integrated assembler, I think we can make it default. We discussed what we need, and we agreed to go with a simple boolean flag that switches both target and host tools: https://lkml.org/lkml/2020/3/28/494 https://lkml.org/lkml/2020/4/3/43 Some items discussed, but not adopted: - LLVM_DIR When multiple versions of LLVM are installed, I just thought supporting LLVM_DIR=/path/to/my/llvm/bin/ might be useful. CC = $(LLVM_DIR)clang LD = $(LLVM_DIR)ld.lld ... However, we can handle this by modifying PATH. So, we decided to not do this. - LLVM_SUFFIX Some distributions (e.g. Debian) package specific versions of LLVM with naming conventions that use the version as a suffix. CC = clang$(LLVM_SUFFIX) LD = ld.lld(LLVM_SUFFIX) ... will allow a user to pass LLVM_SUFFIX=-11 to use clang-11 etc., but the suffixed versions in /usr/bin/ are symlinks to binaries in /usr/lib/llvm-#/bin/, so this can also be handled by PATH. Signed-off-by: Masahiro Yamada Reviewed-by: Nathan Chancellor Tested-by: Nathan Chancellor # build Tested-by: Nick Desaulniers Reviewed-by: Nick Desaulniers Signed-off-by: Nick Desaulniers [nd: conflict in exported vars list from not backporting commit e83b9f55448a ("kbuild: add ability to generate BTF type info for vmlinux")] [nd: hunk against Documentation/kbuild/kbuild.rst dropped due to not backporting commit cd238effefa2 ("docs: kbuild: convert docs to ReST and rename to *.rst")] Signed-off-by: Greg Kroah-Hartman

kbuild: replace AS=clang with LLVM_IAS=1

2020-09-26T16:01:32+00:00

commit 7e20e47c70f810d678d02941fa3c671209c4ca97 upstream. The 'AS' variable is unused for building the kernel. Only the remaining usage is to turn on the integrated assembler. A boolean flag is a better fit for this purpose. AS=clang was added for experts. So, I replaced it with LLVM_IAS=1, breaking the backward compatibility. Suggested-by: Nick Desaulniers Signed-off-by: Masahiro Yamada Reviewed-by: Nathan Chancellor Reviewed-by: Nick Desaulniers Signed-off-by: Nick Desaulniers Signed-off-by: Greg Kroah-Hartman

kbuild: remove AS variable

2020-09-26T16:01:32+00:00

commit aa824e0c962b532d5073cbb41b2efcd6f5e72bae upstream. As commit 5ef872636ca7 ("kbuild: get rid of misleading $(AS) from documents") noted, we rarely use $(AS) directly in the kernel build. Now that the only/last user of $(AS) in drivers/net/wan/Makefile was converted to $(CC), $(AS) is no longer used in the build process. You can still pass in AS=clang, which is just a switch to turn on the LLVM integrated assembler. Signed-off-by: Masahiro Yamada Reviewed-by: Nick Desaulniers Tested-by: Nick Desaulniers Reviewed-by: Nathan Chancellor Signed-off-by: Nick Desaulniers [nd: conflict in exported vars list from not backporting commit e83b9f55448a ("kbuild: add ability to generate BTF type info for vmlinux")] Signed-off-by: Greg Kroah-Hartman

x86/boot: kbuild: allow readelf executable to be specified

2020-09-26T16:01:32+00:00

commit eefb8c124fd969e9a174ff2bedff86aa305a7438 upstream. Introduce a new READELF variable to top-level Makefile, so the name of readelf binary can be specified. Before this change the name of the binary was hardcoded to "$(CROSS_COMPILE)readelf" which might not be present for every toolchain. This allows to build with LLVM Object Reader by using make parameter READELF=llvm-readelf. Link: https://github.com/ClangBuiltLinux/linux/issues/771 Signed-off-by: Dmitry Golovin Reviewed-by: Nick Desaulniers Signed-off-by: Masahiro Yamada Signed-off-by: Nick Desaulniers [nd: conflict in exported vars list from not backporting commit e83b9f55448a ("kbuild: add ability to generate BTF type info for vmlinux")] Signed-off-by: Greg Kroah-Hartman

net: wan: wanxl: use $(M68KCC) instead of $(M68KAS) for rebuilding firmware

2020-09-26T16:01:31+00:00

commit 734f3719d3438f9cc181d674c33ca9762e9148a1 upstream. The firmware source, wanxlfw.S, is currently compiled by the combo of $(CPP) and $(M68KAS). This is not what we usually do for compiling *.S files. In fact, this Makefile is the only user of $(AS) in the kernel build. Instead of combining $(CPP) and (AS) from different tool sets, using $(M68KCC) as an assembler driver is simpler, and saner. Signed-off-by: Masahiro Yamada Signed-off-by: Nick Desaulniers Signed-off-by: Greg Kroah-Hartman