diff options
authorTejun Heo <>2009-09-01 21:12:28 +0900
committerTejun Heo <>2009-09-01 21:23:18 +0900
commit04a13c7c632e1fe04a5f6e6c83565d2559e37598 (patch)
parent142d44b0dd6741a64a7bdbe029110e7c1dcf1d23 (diff)
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: <sysfs_new_dirent+0x30/0x120> 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 <>
1 files changed, 14 insertions, 1 deletions
diff --git a/mm/percpu.c b/mm/percpu.c
index 5fe37842e0e..3311c8919f3 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));