lwn.git/arch/x86/kernel/nmi.c, branch docs-4.16

locking/atomics: COCCINELLE/treewide: Convert trivial ACCESS_ONCE() patterns to READ_ONCE()/WRITE_ONCE()

2017-10-25T09:01:08+00:00

Please do not apply this to mainline directly, instead please re-run the coccinelle script shown below and apply its output. For several reasons, it is desirable to use {READ,WRITE}_ONCE() in preference to ACCESS_ONCE(), and new code is expected to use one of the former. So far, there's been no reason to change most existing uses of ACCESS_ONCE(), as these aren't harmful, and changing them results in churn. However, for some features, the read/write distinction is critical to correct operation. To distinguish these cases, separate read/write accessors must be used. This patch migrates (most) remaining ACCESS_ONCE() instances to {READ,WRITE}_ONCE(), using the following coccinelle script: ---- // Convert trivial ACCESS_ONCE() uses to equivalent READ_ONCE() and // WRITE_ONCE() // $ make coccicheck COCCI=/home/mark/once.cocci SPFLAGS="--include-headers" MODE=patch virtual patch @ depends on patch @ expression E1, E2; @@ - ACCESS_ONCE(E1) = E2 + WRITE_ONCE(E1, E2) @ depends on patch @ expression E; @@ - ACCESS_ONCE(E) + READ_ONCE(E) ---- Signed-off-by: Mark Rutland Signed-off-by: Paul E. McKenney Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: davem@davemloft.net Cc: linux-arch@vger.kernel.org Cc: mpe@ellerman.id.au Cc: shuah@kernel.org Cc: snitzer@redhat.com Cc: thor.thayer@linux.intel.com Cc: tj@kernel.org Cc: viro@zeniv.linux.org.uk Cc: will.deacon@arm.com Link: http://lkml.kernel.org/r/1508792849-3115-19-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar

x86/nmi: Use raw lock

2017-08-16T18:40:09+00:00

register_nmi_handler() can be called from PREEMPT_RT atomic context (e.g. wakeup_cpu_via_init_nmi() or native_stop_other_cpus()), and thus ordinary spinlocks cannot be used. Signed-off-by: Scott Wood Signed-off-by: Thomas Gleixner Acked-by: Don Zickus Link: http://lkml.kernel.org/r/20170724213242.27598-1-swood@redhat.com

Merge tag 'edac_for_4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/bp/bp

2017-05-01T18:36:00+00:00

Pull EDAC updates from Borislav Petkov: - an EDAC driver for Cavium ThunderX RAS IP (Sergey Temerkhanov) - removal of DRAM error reporting through PCI SERR NMI (Borislav Petkov) - misc small fixes (Jan Glauber, Thor Thayer) * tag 'edac_for_4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/bp/bp: EDAC, ghes: Do not enable it by default EDAC: Rename report status accessors EDAC: Delete edac_stub.c EDAC: Update Kconfig help text EDAC: Remove EDAC_MM_EDAC EDAC: Issue tracepoint only when it is defined ACPI/extlog: Add EDAC dependency EDAC: Move edac_op_state to edac_mc.c EDAC: Remove edac_err_assert EDAC: Get rid of edac_handlers x86/nmi, EDAC: Get rid of DRAM error reporting thru PCI SERR NMI EDAC, highbank: Align Makefile directives EDAC, thunderx: Remove unused code EDAC, thunderx: Change LMC index calculation EDAC, altera: Fix peripheral warnings for Cyclone5 EDAC, thunderx: Fix L2C MCI interrupt disable EDAC, thunderx: Add Cavium ThunderX EDAC driver

x86/nmi, EDAC: Get rid of DRAM error reporting thru PCI SERR NMI

2017-04-10T15:13:48+00:00

Apparently, some machines used to report DRAM errors through a PCI SERR NMI. This is why we have a call into EDAC in the NMI handler. See c0d121720220 ("drivers/edac: add new nmi rescan"). From looking at the patch above, that's two drivers: e752x_edac.c and e7xxx_edac.c. Now, I wanna say those are old machines which are probably decommissioned already. Tony says that "[t]the newest CPU supported by either of those drivers is the Xeon E7520 (a.k.a. "Nehalem") released in Q1'2010. Possibly some folks are still using these ... but people that hold onto h/w for 7 years generally cling to old s/w too ... so I'd guess it unlikely that we will get complaints for breaking these in upstream." So even if there is a small number still in use, we did load EDAC with edac_op_state == EDAC_OPSTATE_POLL by default (we still do, in fact) which means a default EDAC setup without any parameters supplied on the command line or otherwise would never even log the error in the NMI handler because we're polling by default: inline int edac_handler_set(void) { if (edac_op_state == EDAC_OPSTATE_POLL) return 0; return atomic_read(&edac_handlers); } So, long story short, I'd like to get rid of that nastiness called edac_stub.c and confine all the EDAC drivers solely to drivers/edac/. If we ever have to do stuff like that again, it should be notifiers we're using and not some insanity like this one. Signed-off-by: Borislav Petkov Acked-by: Thomas Gleixner Cc: Tony Luck

x86/platform: Remove warning message for duplicate NMI handlers

2017-03-13T19:45:18+00:00

Remove the WARNING message associated with multiple NMI handlers as there are at least two that are legitimate. These are the KGDB and the UV handlers and both want to be called if the NMI has not been claimed by any other NMI handler. Use of the UNKNOWN NMI call chain dramatically lowers the NMI call rate when high frequency NMI tools are in use, notably the perf tools. It is required on systems that cannot sustain a high NMI call rate without adversely affecting the system operation. Signed-off-by: Mike Travis Reviewed-by: Dimitri Sivanich Cc: Don Zickus Cc: Peter Zijlstra Cc: Russ Anderson Cc: Frank Ramsay Cc: Tony Ernst Link: http://lkml.kernel.org/r/20170307210841.730959611@asylum.americas.sgi.com Signed-off-by: Thomas Gleixner

sched/headers: Prepare for new header dependencies before moving code to

2017-03-02T07:42:34+00:00

We are going to split out of , which will have to be picked up from other headers and a couple of .c files. Create a trivial placeholder file that just maps to to make this patch obviously correct and bisectable. Include the new header in the files that are going to need it. Acked-by: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar

sched/headers: Prepare for new header dependencies before moving code to

2017-03-02T07:42:27+00:00

We are going to split out of , which will have to be picked up from other headers and .c files. Create a trivial placeholder file that just maps to to make this patch obviously correct and bisectable. Include the new header in the files that are going to need it. Acked-by: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar

x86: include linux/ratelimit.h in nmi.c

2016-06-06T15:10:15+00:00

When building random configurations, we now occasionally get a new build error: In file included from include/linux/kernel.h:13:0, from include/linux/list.h:8, from include/linux/preempt.h:10, from include/linux/spinlock.h:50, from arch/x86/kernel/nmi.c:13: arch/x86/kernel/nmi.c: In function 'nmi_max_handler': include/linux/printk.h:375:9: error: type defaults to 'int' in declaration of 'DEFINE_RATELIMIT_STATE' [-Werror=implicit-int] static DEFINE_RATELIMIT_STATE(_rs, \ ^ arch/x86/kernel/nmi.c:110:2: note: in expansion of macro 'printk_ratelimited' printk_ratelimited(KERN_INFO ^~~~~~~~~~~~~~~~~~ This was working before the rtc rework series because linux/ratelimit.h was included implictly through asm/mach_traps.h -> asm/mc146818rtc.h -> linux/mc146818rtc.h -> linux/rtc.h -> linux/device.h. We clearly shouldn't rely on this indirect inclusion, so this adds an explicit #include in the file that needs it. Signed-off-by: Arnd Bergmann Reported-by: kbuild test robot Acked-by: Thomas Gleixner Fixes: 5ab788d73832 ("rtc: cmos: move mc146818rtc code out of asm-generic/rtc.h") Signed-off-by: Alexandre Belloni

x86/nmi: Mark 'ignore_nmis' as __read_mostly

2016-03-08T11:48:19+00:00

ignore_nmis is used in two distinct places: 1. modified through {stop,restart}_nmi by alternative_instructions 2. read by do_nmi to determine if default_do_nmi should be called or not thus the access pattern conforms to __read_mostly and do_nmi() is a fastpath. Signed-off-by: Kostenzer Felix Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar

x86/nmi: Save regs in crash dump on external NMI

2015-12-19T10:07:01+00:00

Now, multiple CPUs can receive an external NMI simultaneously by specifying the "apic_extnmi=all" command line parameter. When we take a crash dump by using external NMI with this option, we fail to save registers into the crash dump. This happens as follows: CPU 0 CPU 1 ================================ ============================= receive an external NMI default_do_nmi() receive an external NMI spin_lock(&nmi_reason_lock) default_do_nmi() io_check_error() spin_lock(&nmi_reason_lock) panic() busy loop ... kdump_nmi_shootdown_cpus() issue NMI IPI -----------> blocked until IRET busy loop... Here, since CPU 1 is in NMI context, an additional NMI from CPU 0 remains unhandled until CPU 1 IRETs. However, CPU 1 will never execute IRET so the NMI is not handled and the callback function to save registers is never called. To solve this issue, we check if the IPI for crash dumping was issued while waiting for nmi_reason_lock to be released, and if so, call its callback function directly. If the IPI is not issued (e.g. kdump is disabled), the actual behavior doesn't change. Signed-off-by: Hidehiro Kawai Acked-by: Michal Hocko Cc: Andrew Morton Cc: Andy Lutomirski Cc: Baoquan He Cc: Dave Young Cc: "Eric W. Biederman" Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Jiang Liu Cc: Jonathan Corbet Cc: kexec@lists.infradead.org Cc: linux-doc@vger.kernel.org Cc: Masami Hiramatsu Cc: Peter Zijlstra Cc: Stefan Lippers-Hollmann Cc: Steven Rostedt Cc: Thomas Gleixner Cc: Vivek Goyal Cc: x86-ml Link: http://lkml.kernel.org/r/20151210065245.4587.39316.stgit@softrs Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner