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| Started by | Byungchul Park <byungchul.park@lge.com> |
|---|---|
| First post | 2016-01-18 02:00 +0100 |
| Last post | 2016-01-27 03:30 +0100 |
| Articles | 7 — 3 participants |
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[PATCH v2] lib/spinlock_debug.c: prevent an infinite recursive cycle in spin_dump() Byungchul Park <byungchul.park@lge.com> - 2016-01-18 02:00 +0100
Re: [PATCH v2] lib/spinlock_debug.c: prevent an infinite recursive cycle in spin_dump() Byungchul Park <byungchul.park@lge.com> - 2016-01-19 03:00 +0100
Re: [PATCH v2] lib/spinlock_debug.c: prevent an infinite recursive cycle in spin_dump() Byungchul Park <byungchul.park@lge.com> - 2016-01-21 09:20 +0100
Re: [PATCH v2] lib/spinlock_debug.c: prevent an infinite recursive cycle in spin_dump() Andrew Morton <akpm@linux-foundation.org> - 2016-01-27 01:20 +0100
Re: [PATCH v2] lib/spinlock_debug.c: prevent an infinite recursive cycle in spin_dump() Peter Hurley <peter@hurleysoftware.com> - 2016-01-27 02:20 +0100
Re: [PATCH v2] lib/spinlock_debug.c: prevent an infinite recursive cycle in spin_dump() Byungchul Park <byungchul.park@lge.com> - 2016-01-27 03:10 +0100
Re: [PATCH v2] lib/spinlock_debug.c: prevent an infinite recursive cycle in spin_dump() Byungchul Park <byungchul.park@lge.com> - 2016-01-27 03:30 +0100
| From | Byungchul Park <byungchul.park@lge.com> |
|---|---|
| Date | 2016-01-18 02:00 +0100 |
| Subject | [PATCH v2] lib/spinlock_debug.c: prevent an infinite recursive cycle in spin_dump() |
| Message-ID | <qS6kO-1AW-3@gated-at.bofh.it> |
It causes an infinite recursive cycle when using CONFIG_DEBUG_SPINLOCK,
in the spin_dump(). Backtrace prints printk() -> console_trylock() ->
do_raw_spin_lock() -> spint_bug() -> spin_dump() -> printk()...
infinitely.
If the spin_bug() is called from a function like printk() which is
trying to obtain the console lock, we should prevent the debug spinlock
code from calling printk() again in that context.
Signed-off-by: Byungchul Park <byungchul.park@lge.com>
---
kernel/locking/spinlock_debug.c | 11 +++++++++++
kernel/printk/printk.c | 5 +++++
2 files changed, 16 insertions(+)
diff --git a/kernel/locking/spinlock_debug.c b/kernel/locking/spinlock_debug.c
index 0374a59..e745973 100644
--- a/kernel/locking/spinlock_debug.c
+++ b/kernel/locking/spinlock_debug.c
@@ -67,11 +67,22 @@ static void spin_dump(raw_spinlock_t *lock, const char *msg)
dump_stack();
}
+extern int is_console_lock(raw_spinlock_t *lock);
+
static void spin_bug(raw_spinlock_t *lock, const char *msg)
{
if (!debug_locks_off())
return;
+ /*
+ * If this function is called from a function like printk()
+ * which is trying to obtain the console lock, then we should
+ * not call printk() any more. Or it will cause an infinite
+ * recursive cycle!
+ */
+ if (unlikely(is_console_lock(lock)))
+ return;
+
spin_dump(lock, msg);
}
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 2ce8826..50ea552 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -119,6 +119,11 @@ static int __down_trylock_console_sem(unsigned long ip)
up(&console_sem);\
} while (0)
+int is_console_lock(raw_spinlock_t *lock)
+{
+ return &console_sem.lock == lock;
+}
+
/*
* This is used for debugging the mess that is the VT code by
* keeping track if we have the console semaphore held. It's
--
1.9.1
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| From | Byungchul Park <byungchul.park@lge.com> |
|---|---|
| Date | 2016-01-19 03:00 +0100 |
| Subject | Re: [PATCH v2] lib/spinlock_debug.c: prevent an infinite recursive cycle in spin_dump() |
| Message-ID | <qStKq-Kn-7@gated-at.bofh.it> |
| In reply to | #1311208 |
I missed the version change desciption when I sent this v2. This patch worked for me. Please let me know if you have other opinions. Changes from v1 to v2 - only change comment and commit message esp. replacing "deadlock" with "infinite recursive cycle", since it is not an actual deadlock. Thanks, Byungchul
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| From | Byungchul Park <byungchul.park@lge.com> |
|---|---|
| Date | 2016-01-21 09:20 +0100 |
| Subject | Re: [PATCH v2] lib/spinlock_debug.c: prevent an infinite recursive cycle in spin_dump() |
| Message-ID | <qTiDg-2B3-7@gated-at.bofh.it> |
| In reply to | #1311890 |
On Tue, Jan 19, 2016 at 10:53:56AM +0900, Byungchul Park wrote: > I missed the version change desciption when I sent this v2. This patch > worked for me. Please let me know if you have other opinions. > > Changes from v1 to v2 > - only change comment and commit message esp. replacing "deadlock" > with "infinite recursive cycle", since it is not an actual deadlock. I was careless. I think it should be fixed by another way, instead of the way this patch suggested. > > Thanks, > Byungchul
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| From | Andrew Morton <akpm@linux-foundation.org> |
|---|---|
| Date | 2016-01-27 01:20 +0100 |
| Subject | Re: [PATCH v2] lib/spinlock_debug.c: prevent an infinite recursive cycle in spin_dump() |
| Message-ID | <qVm01-3EK-1@gated-at.bofh.it> |
| In reply to | #1311208 |
On Mon, 18 Jan 2016 09:58:12 +0900 Byungchul Park <byungchul.park@lge.com> wrote:
> It causes an infinite recursive cycle when using CONFIG_DEBUG_SPINLOCK,
> in the spin_dump(). Backtrace prints printk() -> console_trylock() ->
> do_raw_spin_lock() -> spint_bug() -> spin_dump() -> printk()...
> infinitely.
>
> If the spin_bug() is called from a function like printk() which is
> trying to obtain the console lock, we should prevent the debug spinlock
> code from calling printk() again in that context.
>
lol. Excellent.
> --- a/kernel/locking/spinlock_debug.c
> +++ b/kernel/locking/spinlock_debug.c
> @@ -67,11 +67,22 @@ static void spin_dump(raw_spinlock_t *lock, const char *msg)
> dump_stack();
> }
>
> +extern int is_console_lock(raw_spinlock_t *lock);
> +
> static void spin_bug(raw_spinlock_t *lock, const char *msg)
> {
> if (!debug_locks_off())
> return;
>
> + /*
> + * If this function is called from a function like printk()
> + * which is trying to obtain the console lock, then we should
> + * not call printk() any more. Or it will cause an infinite
> + * recursive cycle!
> + */
> + if (unlikely(is_console_lock(lock)))
> + return;
> +
> spin_dump(lock, msg);
> }
>
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 2ce8826..50ea552 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -119,6 +119,11 @@ static int __down_trylock_console_sem(unsigned long ip)
> up(&console_sem);\
> } while (0)
>
> +int is_console_lock(raw_spinlock_t *lock)
> +{
> + return &console_sem.lock == lock;
> +}
> +
> /*
> * This is used for debugging the mess that is the VT code by
> * keeping track if we have the console semaphore held. It's
I can't immediately think of anything better than this. It's a hack, but
it's a small and quite clear hack.
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| From | Peter Hurley <peter@hurleysoftware.com> |
|---|---|
| Date | 2016-01-27 02:20 +0100 |
| Subject | Re: [PATCH v2] lib/spinlock_debug.c: prevent an infinite recursive cycle in spin_dump() |
| Message-ID | <qVmW6-4h1-9@gated-at.bofh.it> |
| In reply to | #1318490 |
On 01/26/2016 04:11 PM, Andrew Morton wrote: > On Mon, 18 Jan 2016 09:58:12 +0900 Byungchul Park <byungchul.park@lge.com> wrote: > >> It causes an infinite recursive cycle when using CONFIG_DEBUG_SPINLOCK, >> in the spin_dump(). Backtrace prints printk() -> console_trylock() -> >> do_raw_spin_lock() -> spint_bug() -> spin_dump() -> printk()... >> infinitely. >> >> If the spin_bug() is called from a function like printk() which is >> trying to obtain the console lock, we should prevent the debug spinlock >> code from calling printk() again in that context. >> > > lol. Excellent. [...] > I can't immediately think of anything better than this. It's a hack, but > it's a small and quite clear hack. Andrew, I think you may have missed this follow-up from Byungchul: On 01/21/2016 12:12 AM, Byungchul Park wrote: > I was careless. I think it should be fixed by another way, instead of > the way this patch suggested. Regards, Peter Hurley
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| From | Byungchul Park <byungchul.park@lge.com> |
|---|---|
| Date | 2016-01-27 03:10 +0100 |
| Subject | Re: [PATCH v2] lib/spinlock_debug.c: prevent an infinite recursive cycle in spin_dump() |
| Message-ID | <qVnIu-4QH-9@gated-at.bofh.it> |
| In reply to | #1318490 |
On Tue, Jan 26, 2016 at 04:11:24PM -0800, Andrew Morton wrote: > I can't immediately think of anything better than this. It's a hack, but > it's a small and quite clear hack. I am sorry for making you confused. :( I think I need to find another way to solve this problem. At first, when I wrote this patch, I was also confused. thanks, byungchul
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| From | Byungchul Park <byungchul.park@lge.com> |
|---|---|
| Date | 2016-01-27 03:30 +0100 |
| Subject | Re: [PATCH v2] lib/spinlock_debug.c: prevent an infinite recursive cycle in spin_dump() |
| Message-ID | <qVo1Q-4Y0-11@gated-at.bofh.it> |
| In reply to | #1318550 |
On Wed, Jan 27, 2016 at 11:00:14AM +0900, Byungchul Park wrote: > On Tue, Jan 26, 2016 at 04:11:24PM -0800, Andrew Morton wrote: > > I can't immediately think of anything better than this. It's a hack, but > > it's a small and quite clear hack. > > I am sorry for making you confused. :( I think I need to find another way > to solve this problem. At first, when I wrote this patch, I was also > confused. Even though this can fix symptoms.. > > thanks, > byungchul
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