[patch 4/3] fastboot: hold the BKL over the async init call sequence

From: Arjan van de Ven <[email protected]>
Subject: [PATCH] fastboot: sync the async execution before late_initcall and move level 6s (sync) first

Rene Herman points out several cases where it's basically needed to have all
level 6/6a/6s calls done before the level 7 (late_initcall) code runs. This patch
adds a sync point in the transition from the 6's to the 7's.

Second, this patch makes sure that level 6s (sync) happens before the async code starts,
and puts a user in driver/pci in this category that needs to happen before device init.

Signed-off-by: Arjan van de Ven <[email protected]>
---
drivers/pci/pci.c | 2 +-
include/asm-generic/vmlinux.lds.h | 3 ++-
init/main.c | 8 +++++++-
3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 44a46c9..d75295d 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1889,7 +1889,7 @@ static int __devinit pci_setup(char *str)
}
early_param("pci", pci_setup);

-device_initcall(pci_init);
+device_initcall_sync(pci_init);

EXPORT_SYMBOL(pci_reenable_device);
EXPORT_SYMBOL(pci_enable_device_io);
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 39c1afc..514dbdf 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -372,11 +372,12 @@
*(.initcall5.init) \
*(.initcall5s.init) \
*(.initcallrootfs.init) \
+ *(.initcall6s.init) \
__async_initcall_start = .; \
*(.initcall6a.init) \
__async_initcall_end = .; \
*(.initcall6.init) \
- *(.initcall6s.init) \
+ __device_initcall_end = .; \
*(.initcall7.init) \
*(.initcall7s.init)

diff --git a/init/main.c b/init/main.c
index dcb2c32..5c9e90e 100644
--- a/init/main.c
+++ b/init/main.c
@@ -741,6 +741,7 @@ int do_one_initcall(initcall_t fn)

extern initcall_t __initcall_start[], __initcall_end[];
extern initcall_t __async_initcall_start[], __async_initcall_end[];
+extern initcall_t __device_initcall_end[];

static void __init do_async_initcalls(struct work_struct *dummy)
{
@@ -764,7 +765,7 @@ static void __init do_initcalls(void)
{
initcall_t *call;
static DECLARE_WORK(async_work, do_async_initcalls);
- int phase = 0; /* 0 = levels 0 - 6, 1 = level 6a, 2 = after level 6a */
+ int phase = 0; /* 0 = levels 0 - 6, 1 = level 6a, 2 = after level 6a, 3 = after level 6 */

async_init_wq = create_singlethread_workqueue("kasyncinit");

@@ -775,6 +776,11 @@ static void __init do_initcalls(void)
}
if (phase == 1 && call >= __async_initcall_end)
phase = 2;
+ if (phase == 2 && call >= __device_initcall_end) {
+ phase = 3;
+ /* make sure all async work is done before level 7 */
+ flush_workqueue(async_init_wq);
+ }
if (phase != 1)
do_one_initcall(*call);
}
--
1.5.5.1

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* Arjan van de Ven <[email protected]> wrote:

> From: Arjan van de Ven <[email protected]>
> Subject: [PATCH] fastboot: sync the async execution before late_initcall and move level 6s (sync) first
>
> Rene Herman points out several cases where it's basically needed to
> have all level 6/6a/6s calls done before the level 7 (late_initcall)
> code runs. This patch adds a sync point in the transition from the 6's
> to the 7's.
>
> Second, this patch makes sure that level 6s (sync) happens before the
> async code starts, and puts a user in driver/pci in this category that
> needs to happen before device init.

incidentally, this fixed an USB related boot hang i found today on one
of my testsystems running tip/master (which had patches 1-2-3 already),
which i was about to report. Good spotting Rene! I've applied patches
4/5 to tip/fastboot.

Ingo
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On Sun, 2008-07-20 at 09:00 -0700, Arjan van de Ven wrote:
> @@ -775,6 +776,11 @@ static void __init do_initcalls(void)
> }
> if (phase == 1 && call >= __async_initcall_end)
> phase = 2;
> + if (phase == 2 && call >= __device_initcall_end) {
> + phase = 3;
> + /* make sure all async work is done before level 7 */
> + flush_workqueue(async_init_wq);
> + }
> if (phase != 1)
> do_one_initcall(*call);
> }

Did this impact the boot time improvements at all?

Daniel

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On 20/07/08 22:14, Daniel Walker wrote:
> On Sun, 2008-07-20 at 09:00 -0700, Arjan van de Ven wrote:
>> @@ -775,6 +776,11 @@ static void __init do_initcalls(void)
>> }
>> if (phase == 1 && call >= __async_initcall_end)
>> phase = 2;
>> + if (phase == 2 && call >= __device_initcall_end) {
>> + phase = 3;
>> + /* make sure all async work is done before level 7 */
>> + flush_workqueue(async_init_wq);
>> + }
>> if (phase != 1)
>> do_one_initcall(*call);
>> }
>
> Did this impact the boot time improvements at all?

The USB HCD initcalls take so little time to complete (100ms
each) that ensuring they have finished makes no difference.

USB devices get detected after those initcalls finish in
parallel with the rest of the boot process (and there's
about 1.5s before the first USB device driver initcall
runs).

--
Simon Arlott
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