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| author | Chris Metcalf <cmetcalf@ezchip.com> | 2015-03-30 16:33:00 -0400 |
|---|---|---|
| committer | Chris Metcalf <cmetcalf@ezchip.com> | 2015-04-17 14:01:41 -0400 |
| commit | 128f3cb9398b5eeb4ee04b60bd5e314f5c122821 (patch) | |
| tree | a9cb1e04a11883d1ad9587779155cdd82d67958f | |
| parent | 437d3e124d25daaa671bfecfd4015ecd2503a955 (diff) | |
| download | linux-128f3cb9398b5eeb4ee04b60bd5e314f5c122821.tar.bz2 | |
tile: nohz: warn if nohz_full uses hypervisor shared cores
The "hypervisor shared" cores are ones that the Tilera hypervisor
uses to receive interrupts to manage hypervisor-owned devices.
It's a bad idea to try to use those cores with nohz_full, since
they will get interrupted unpredictably -- and invisibly to Linux
tracing tools, since the interrupts are delivered at a higher
privilege level to the Tilera hypervisor.
Generate a clear warning at boot up that this doesn't end well
for the nohz_full cores in question.
Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
| -rw-r--r-- | arch/tile/include/hv/hypervisor.h | 6 | ||||
| -rw-r--r-- | arch/tile/kernel/setup.c | 23 |
2 files changed, 28 insertions, 1 deletions
diff --git a/arch/tile/include/hv/hypervisor.h b/arch/tile/include/hv/hypervisor.h index dfcdeb61ba34..e0e6af4e783b 100644 --- a/arch/tile/include/hv/hypervisor.h +++ b/arch/tile/include/hv/hypervisor.h @@ -961,7 +961,11 @@ typedef enum { HV_INQ_TILES_HFH_CACHE = 2, /** The set of tiles that can be legally used as a LOTAR for a PTE. */ - HV_INQ_TILES_LOTAR = 3 + HV_INQ_TILES_LOTAR = 3, + + /** The set of "shared" driver tiles that the hypervisor may + * periodically interrupt. */ + HV_INQ_TILES_SHARED = 4 } HV_InqTileSet; /** Returns specific information about various sets of tiles within the diff --git a/arch/tile/kernel/setup.c b/arch/tile/kernel/setup.c index f1f579914952..7833b2ccdfbc 100644 --- a/arch/tile/kernel/setup.c +++ b/arch/tile/kernel/setup.c @@ -32,6 +32,7 @@ #include <linux/hugetlb.h> #include <linux/start_kernel.h> #include <linux/screen_info.h> +#include <linux/tick.h> #include <asm/setup.h> #include <asm/sections.h> #include <asm/cacheflush.h> @@ -1390,6 +1391,28 @@ static int __init dataplane(char *str) early_param("dataplane", dataplane); +#ifdef CONFIG_NO_HZ_FULL +/* Warn if hypervisor shared cpus are marked as nohz_full. */ +static int __init check_nohz_full_cpus(void) +{ + struct cpumask shared; + int cpu; + + if (hv_inquire_tiles(HV_INQ_TILES_SHARED, + (HV_VirtAddr) shared.bits, sizeof(shared)) < 0) { + pr_warn("WARNING: No support for inquiring hv shared tiles\n"); + return 0; + } + for_each_cpu(cpu, &shared) { + if (tick_nohz_full_cpu(cpu)) + pr_warn("WARNING: nohz_full cpu %d receives hypervisor interrupts!\n", + cpu); + } + return 0; +} +arch_initcall(check_nohz_full_cpus); +#endif + #ifdef CONFIG_CMDLINE_BOOL static char __initdata builtin_cmdline[COMMAND_LINE_SIZE] = CONFIG_CMDLINE; #endif |