----- Original Message -----
>
> ----- Original Message -----
> >
> > Current code is setting {hard,soft}irq_ctx[] to (irq_ctx **), because
> > per_cpu symbol itself is pointer of specified type (irq_ctx *).
> >
> > But, I wonder how this works in past, the code is expecting
> > {hard,soft}_ctx[] are (irq_ctx *). This fixes by deref per_cpu in
> > initialization, and set expected pointers.
> >
> > Tested on i386 v3.10.
> >
>
> You are correct -- apparently it never did work.
>
> The reason why I never noticed with RHEL kernels is that up until
> linux-2.6.29,
> the IRQ stacks were declared as a static NR_CPUS-bounded array:
>
> #ifdef CONFIG_4KSTACKS
> /*
> * per-CPU IRQ handling contexts (thread information and stack)
> */
> union irq_ctx {
> struct thread_info tinfo;
> u32 stack[THREAD_SIZE/sizeof(u32)];
> };
>
> static union irq_ctx *hardirq_ctx[NR_CPUS] __read_mostly;
> static union irq_ctx *softirq_ctx[NR_CPUS] __read_mostly;
>
> static char softirq_stack[NR_CPUS * THREAD_SIZE] __page_aligned_bss;
> static char hardirq_stack[NR_CPUS * THREAD_SIZE] __page_aligned_bss;
>
>
> Then in linux-2.6.30, they were changed to be per-cpu variables:
>
> #ifdef CONFIG_4KSTACKS
> /*
> * per-CPU IRQ handling contexts (thread information and stack)
> */
> union irq_ctx {
> struct thread_info tinfo;
> u32 stack[THREAD_SIZE/sizeof(u32)];
> } __attribute__((aligned(PAGE_SIZE)));
>
> static DEFINE_PER_CPU(union irq_ctx *, hardirq_ctx);
> static DEFINE_PER_CPU(union irq_ctx *, softirq_ctx);
>
> static DEFINE_PER_CPU_PAGE_ALIGNED(union irq_ctx, hardirq_stack);
> static DEFINE_PER_CPU_PAGE_ALIGNED(union irq_ctx, softirq_stack);
>
> We never ran into the bug in 32-bit x86 RHEL6 (2.6.32-based) kernels because
> we did not configure CONFIG_4KSTACKS.
>
> Later on, the CONFIG_4KSTACKS restriction looks like it was removed, but we
> stopped supporting 32-bit x86 in RHEL7. And nobody ever reported it from any
> other x86 kernel sources.
>
> I also note that in linux-3.15 the data structure name and variables were
> changed to:
>
> struct irq_stack {
> u32 stack[THREAD_SIZE/sizeof(u32)];
> } __aligned(THREAD_SIZE);
>
> DECLARE_PER_CPU(struct irq_stack *, hardirq_stack);
> DECLARE_PER_CPU(struct irq_stack *, softirq_stack);
>
> So your patch would need more work for 3.15 and later kernels.
>
> Thanks,
> Dave
Hi Ogawa,
Please review the attached update to your patch, which adds support for
the irq_ctx-to-irq_stack transition.
Thanks,
Dave
diff --git a/task.c b/task.c
index 95d9130..661c104 100644
--- a/task.c
+++ b/task.c
@@ -567,13 +567,24 @@ irqstacks_init(void)
thread_info_buf = GETBUF(SIZE(irq_ctx));
- if ((hard_sp = per_cpu_symbol_search("per_cpu__hardirq_ctx"))) {
+ if ((hard_sp = per_cpu_symbol_search("per_cpu__hardirq_ctx")) ||
+ (hard_sp = per_cpu_symbol_search("per_cpu__hardirq_stack"))) {
if ((kt->flags & SMP) && (kt->flags & PER_CPU_OFF)) {
for (i = 0; i < NR_CPUS; i++) {
+ ulong ptr;
+
if (!kt->__per_cpu_offset[i])
continue;
- tt->hardirq_ctx[i] = hard_sp->value +
- kt->__per_cpu_offset[i];
+ ptr = hard_sp->value + kt->__per_cpu_offset[i];
+
+ if (!readmem(ptr, KVADDR, &ptr,
+ sizeof(void *), "hardirq ctx",
+ RETURN_ON_ERROR)) {
+ error(INFO, "cannot read hardirq_ctx[%d] at %lx\n",
+ i, ptr);
+ continue;
+ }
+ tt->hardirq_ctx[i] = ptr;
}
} else
tt->hardirq_ctx[0] = hard_sp->value;
@@ -585,29 +596,42 @@ irqstacks_init(void)
} else
error(WARNING, "cannot determine hardirq_ctx addresses\n");
- for (i = 0; i < NR_CPUS; i++) {
- if (!(tt->hardirq_ctx[i]))
- continue;
+ if (MEMBER_EXISTS("irq_ctx", "tinfo")) {
+ for (i = 0; i < NR_CPUS; i++) {
+ if (!(tt->hardirq_ctx[i]))
+ continue;
- if (!readmem(tt->hardirq_ctx[i], KVADDR, thread_info_buf,
- SIZE(irq_ctx), "hardirq thread_union",
- RETURN_ON_ERROR)) {
- error(INFO, "cannot read hardirq_ctx[%d] at %lx\n",
- i, tt->hardirq_ctx[i]);
- continue;
- }
+ if (!readmem(tt->hardirq_ctx[i], KVADDR, thread_info_buf,
+ SIZE(irq_ctx), "hardirq thread_union",
+ RETURN_ON_ERROR)) {
+ error(INFO, "cannot read hardirq_ctx[%d] at %lx\n",
+ i, tt->hardirq_ctx[i]);
+ continue;
+ }
- tt->hardirq_tasks[i] =
- ULONG(thread_info_buf+OFFSET(thread_info_task));
+ tt->hardirq_tasks[i] =
+ ULONG(thread_info_buf+OFFSET(thread_info_task));
+ }
}
- if ((soft_sp = per_cpu_symbol_search("per_cpu__softirq_ctx"))) {
+ if ((soft_sp = per_cpu_symbol_search("per_cpu__softirq_ctx")) ||
+ (soft_sp = per_cpu_symbol_search("per_cpu__softirq_stack"))) {
if ((kt->flags & SMP) && (kt->flags & PER_CPU_OFF)) {
for (i = 0; i < NR_CPUS; i++) {
+ ulong ptr;
+
if (!kt->__per_cpu_offset[i])
continue;
- tt->softirq_ctx[i] = soft_sp->value +
- kt->__per_cpu_offset[i];
+ ptr = soft_sp->value + kt->__per_cpu_offset[i];
+
+ if (!readmem(ptr, KVADDR, &ptr,
+ sizeof(void *), "softirq ctx",
+ RETURN_ON_ERROR)) {
+ error(INFO, "cannot read softirq_ctx[%d] at %lx\n",
+ i, ptr);
+ continue;
+ }
+ tt->softirq_ctx[i] = ptr;
}
} else
tt->softirq_ctx[0] = soft_sp->value;
@@ -619,21 +643,23 @@ irqstacks_init(void)
} else
error(WARNING, "cannot determine softirq_ctx addresses\n");
- for (i = 0; i < NR_CPUS; i++) {
- if (!(tt->softirq_ctx[i]))
- continue;
-
- if (!readmem(tt->softirq_ctx[i], KVADDR, thread_info_buf,
- SIZE(irq_ctx), "softirq thread_union",
- RETURN_ON_ERROR)) {
- error(INFO, "cannot read softirq_ctx[%d] at %lx\n",
- i, tt->hardirq_ctx[i]);
- continue;
- }
-
- tt->softirq_tasks[i] =
- ULONG(thread_info_buf+OFFSET(thread_info_task));
- }
+ if (MEMBER_EXISTS("irq_ctx", "tinfo")) {
+ for (i = 0; i < NR_CPUS; i++) {
+ if (!(tt->softirq_ctx[i]))
+ continue;
+
+ if (!readmem(tt->softirq_ctx[i], KVADDR, thread_info_buf,
+ SIZE(irq_ctx), "softirq thread_union",
+ RETURN_ON_ERROR)) {
+ error(INFO, "cannot read softirq_ctx[%d] at %lx\n",
+ i, tt->hardirq_ctx[i]);
+ continue;
+ }
+
+ tt->softirq_tasks[i] =
+ ULONG(thread_info_buf+OFFSET(thread_info_task));
+ }
+ }
tt->flags |= IRQSTACKS;
diff --git a/x86.c b/x86.c
index 54ce7a5..27bf0ea 100644
--- a/x86.c
+++ b/x86.c
@@ -1963,6 +1963,8 @@ x86_init(int when)
STRUCT_SIZE_INIT(e820map, "e820map");
STRUCT_SIZE_INIT(e820entry, "e820entry");
STRUCT_SIZE_INIT(irq_ctx, "irq_ctx");
+ if (!VALID_STRUCT(irq_ctx))
+ STRUCT_SIZE_INIT(irq_ctx, "irq_stack");
MEMBER_OFFSET_INIT(e820map_nr_map, "e820map", "nr_map");
MEMBER_OFFSET_INIT(e820entry_addr, "e820entry", "addr");
MEMBER_OFFSET_INIT(e820entry_size, "e820entry", "size");
--
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