From 04a13c7c632e1fe04a5f6e6c83565d2559e37598 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Tue, 1 Sep 2009 21:12:28 +0900 Subject: [PATCH] percpu: don't assume existence of cpu0 percpu incorrectly assumed that cpu0 was always there which led to the following warning and eventual oops on sparc machines w/o cpu0. WARNING: at mm/percpu.c:651 pcpu_map+0xdc/0x100() Modules linked in: Call Trace: [000000000045eb70] warn_slowpath_common+0x50/0xa0 [000000000045ebdc] warn_slowpath_null+0x1c/0x40 [00000000004d493c] pcpu_map+0xdc/0x100 [00000000004d59a4] pcpu_alloc+0x3e4/0x4e0 [00000000004d5af8] __alloc_percpu+0x18/0x40 [00000000005b112c] __percpu_counter_init+0x4c/0xc0 ... Unable to handle kernel NULL pointer dereference ... I7: Disabling lock debugging due to kernel taint Caller[000000000053c1b0]: sysfs_new_dirent+0x30/0x120 Caller[000000000053c7a4]: create_dir+0x24/0xc0 Caller[000000000053c870]: sysfs_create_dir+0x30/0x80 Caller[00000000005990e8]: kobject_add_internal+0xc8/0x200 ... Kernel panic - not syncing: Attempted to kill the idle task! This patch fixes the problem by backporting parts from devel branch to make percpu core not depend on the existence of cpu0. Signed-off-by: Tejun Heo Reported-by: Meelis Roos Cc: David Miller --- mm/percpu.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/mm/percpu.c b/mm/percpu.c index 5fe37842e0ea..3311c8919f37 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -197,7 +197,12 @@ static unsigned long pcpu_chunk_addr(struct pcpu_chunk *chunk, static bool pcpu_chunk_page_occupied(struct pcpu_chunk *chunk, int page_idx) { - return *pcpu_chunk_pagep(chunk, 0, page_idx) != NULL; + /* + * Any possible cpu id can be used here, so there's no need to + * worry about preemption or cpu hotplug. + */ + return *pcpu_chunk_pagep(chunk, raw_smp_processor_id(), + page_idx) != NULL; } /* set the pointer to a chunk in a page struct */ @@ -297,6 +302,14 @@ static struct pcpu_chunk *pcpu_chunk_addr_search(void *addr) return pcpu_first_chunk; } + /* + * The address is relative to unit0 which might be unused and + * thus unmapped. Offset the address to the unit space of the + * current processor before looking it up in the vmalloc + * space. Note that any possible cpu id can be used here, so + * there's no need to worry about preemption or cpu hotplug. + */ + addr += raw_smp_processor_id() * pcpu_unit_size; return pcpu_get_page_chunk(vmalloc_to_page(addr)); } -- 2.39.2