The patch titled
Subject: mm/percpu.c: fix panic triggered by BUG_ON() falsely
has been added to the -mm tree. Its filename is
mm-percpuc-fix-panic-triggered-by-bug_on-falsely.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-percpuc-fix-panic-triggered-by-bug_on-falsely.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-percpuc-fix-panic-triggered-by-bug_on-falsely.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: zijun_hu <zijun_hu@xxxxxxx>
Subject: mm/percpu.c: fix panic triggered by BUG_ON() falsely
As shown by pcpu_build_alloc_info(), the number of units within a percpu
group is deduced by rounding up the number of CPUs within the group to
@upa boundary/ Therefore, the number of CPUs isn't equal to the units's if
it isn't aligned to @upa normally. However, pcpu_page_first_chunk() uses
BUG_ON() to assert that one number is equal to the other roughly, so a
panic is maybe triggered by the BUG_ON() incorrectly.
In order to fix this issue, the number of CPUs is rounded up then compared
with units's and the BUG_ON() is replaced with a warning and return of an
error code as well, to keep system alive as much as possible.
Link: http://lkml.kernel.org/r/57FCF07C.2020103@xxxxxxxx
Signed-off-by: zijun_hu <zijun_hu@xxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/percpu.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff -puN mm/percpu.c~mm-percpuc-fix-panic-triggered-by-bug_on-falsely mm/percpu.c
--- a/mm/percpu.c~mm-percpuc-fix-panic-triggered-by-bug_on-falsely
+++ a/mm/percpu.c
@@ -2091,6 +2091,8 @@ int __init pcpu_page_first_chunk(size_t
size_t pages_size;
struct page **pages;
int unit, i, j, rc;
+ int upa;
+ int nr_g0_units;
snprintf(psize_str, sizeof(psize_str), "%luK", PAGE_SIZE >> 10);
@@ -2098,7 +2100,12 @@ int __init pcpu_page_first_chunk(size_t
if (IS_ERR(ai))
return PTR_ERR(ai);
BUG_ON(ai->nr_groups != 1);
- BUG_ON(ai->groups[0].nr_units != num_possible_cpus());
+ upa = ai->alloc_size/ai->unit_size;
+ nr_g0_units = roundup(num_possible_cpus(), upa);
+ if (unlikely(WARN_ON(ai->groups[0].nr_units != nr_g0_units))) {
+ pcpu_free_alloc_info(ai);
+ return -EINVAL;
+ }
unit_pages = ai->unit_size >> PAGE_SHIFT;
@@ -2109,21 +2116,22 @@ int __init pcpu_page_first_chunk(size_t
/* allocate pages */
j = 0;
- for (unit = 0; unit < num_possible_cpus(); unit++)
+ for (unit = 0; unit < num_possible_cpus(); unit++) {
+ unsigned int cpu = ai->groups[0].cpu_map[unit];
for (i = 0; i < unit_pages; i++) {
- unsigned int cpu = ai->groups[0].cpu_map[unit];
void *ptr;
ptr = alloc_fn(cpu, PAGE_SIZE, PAGE_SIZE);
if (!ptr) {
pr_warn("failed to allocate %s page for cpu%u\n",
- psize_str, cpu);
+ psize_str, cpu);
goto enomem;
}
/* kmemleak tracks the percpu allocations separately */
kmemleak_free(ptr);
pages[j++] = virt_to_page(ptr);
}
+ }
/* allocate vm area, map the pages and copy static data */
vm.flags = VM_ALLOC;
_
Patches currently in -mm which might be from zijun_hu@xxxxxxx are
mm-percpuc-fix-panic-triggered-by-bug_on-falsely.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
