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[RFC][PATCH v4 -next 0/4] Make pstore/kmsg_dump run after stopping other cpus in panic path

January 05th, 2012 - 12:40 pm ET by Seiji Aguchi | Report spam
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Hi,

Discussion:
As Don mentioned in following thread, it would be nice for pstore/kmsg_dump to serialize
panic path because they can log messages reliably.

https://lkml.org/lkml/2011/10/13/427

This patchset is based on his proposal switching smp_send_stop() from REBOOT_VECTOR to NMI.

Change Log:

v3 -> v4
- Add comment for explaining the purpose of WARN_ON() based on Don's comment (patch 2/4)
https://lkml.org/lkml/2011/12/12/296

- Skip spin_lock of efi_pstore_write() in panic case based on discussion with Tony (patch 4/4)
https://lkml.org/lkml/2012/1/3/151

- Apply this patchset to -next tree instead of linus -tree so that "patch 4/4" makes simple

v2 -> v3
- Skip spin_locks in panic case in both kmsg_dump() and pstore_dump() instead of calling spin_lock_init()
to avoid potential issues due to spin_lock_init()
- Add WARN_ON() in "in_nmi() and !panic" case into kmsg_dump() so that we trap when someone adds
new kmsg_dump() in NMI path in the future
- Skip subsequent kmsg_dump() function calls to avoid deadlock.

v1 -> v2
- Add trylocks to kmsg_dump()/pstore_dump() so that they can work in NMI context.
- Divide a patch into two
First one is just moving kmsg_dump(KMSG_DUMP_PANIC) below smp_send_stop()
Second one is changing lock operations in kmsg_dump()/pstore_dump()
v1
- Move kmsg_dump(KMSG_DUMP_PANIC) below smp_send_stop
- Bust logbuf_lock of kmsg_dump() in panic path for avoiding deadlock
- Bust psinfo->buf_lock of pstore_dump() in panic path for avoiding deadlock

Patch Description:
[RFC][PATCH v4 -next 1/4] Move kmsg_dump(KMSG_DUMP_PANIC) below smp_send_stop()
- Just move kmsg_dump(KMSG_DUMP_PANIC) below smp_send_stop()

[RFC][PATCH v4 -next 2/4] Skip spin_locks in panic case and Add WARN_ON()
- Skip spin_locks in panic case in both kmsg_dump() and pstore_dump()
- Add WARN_ON() in "in_nmi() and !panic" case into kmsg_dump()

[RFC][PATCH v4 -next 3/4] Skip subsequent kmsg_dump()
- Skip subsequent kmsg_dump() function calls in panic path

[RFC][PATCH v4 -next 4/4] Skip spin_lock of efi_pstore_write() in panic case
- Skip spin_lock of efi_pstore_write() in panic case to avoid deadlock

Seiji
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#1 Seiji Aguchi
January 05th, 2012 - 12:40 pm ET | Report spam
This patch just moves kmsg_dump(KMSG_DUMP_PANIC) below smp_send_stop
for serializing logging process via smp_send_stop.

Signed-off-by: Seiji Aguchi
Acked-by: Don Zickus


kernel/panic.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/panic.c b/kernel/panic.c
index 80aed44..da585b8 100644
a/kernel/panic.c
+++ b/kernel/panic.c
@@ -108,8 +108,6 @@ void panic(const char *fmt, ...)
*/
crash_kexec(NULL);

- kmsg_dump(KMSG_DUMP_PANIC);
-
/*
* Note smp_send_stop is the usual smp shutdown function, which
* unfortunately means it may not be hardened to work in a panic
@@ -117,6 +115,8 @@ void panic(const char *fmt, ...)
*/
smp_send_stop();

+ kmsg_dump(KMSG_DUMP_PANIC);
+
atomic_notifier_call_chain(&panic_notifier_list, 0, buf);

bust_spinlocks(0);
1.7.1

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