Andrew, Dietmar Hahn reported an issue where calling vunmap() on a large (50 GB) region would trigger soft lockup warnings. The following patch would resolve this (by adding a cond_resched() call to vunmap_pmd_range()). Almost calls of vunmap(), unmap_kernel_range() are from process context (as far as I could tell) except for an ACPI driver (drivers/acpi/apei/ghes.c) calls unmap_kernel_range_noflush() from an interrupt and NMI contexts. Can you advise on a preferred solution? For example, an unmap_kernel_page() function (callable from atomic context) could be provided since the GHES driver only maps/unmaps a single page. 8<------------------------- mm/vmalloc: avoid soft lockup warnings when vunmap()'ing large ranges From: David Vrabel <david.vrabel@xxxxxxxxxx> If vunmap() is used to unmap a large (e.g., 50 GB) region, it may take sufficiently long that it triggers soft lockup warnings. Add a cond_resched() into vunmap_pmd_range() so the calling task may be resheduled after unmapping each PMD entry. This is how zap_pmd_range() fixes the same problem for userspace mappings. Reported-by: Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx> Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx> --- mm/vmalloc.c | 1 + 1 files changed, 1 insertions(+), 0 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 0fdf968..b1b5b39 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -75,6 +75,7 @@ static void vunmap_pmd_range(pud_t *pud, unsigned long addr, unsigned long end) if (pmd_none_or_clear_bad(pmd)) continue; vunmap_pte_range(pmd, addr, next); + cond_resched(); } while (pmd++, addr = next, addr != end); } -- 1.7.2.5 -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
