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pstore: change mutex locking to spin_locks

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pstore was using mutex locking to protect read/write access to the
backend plug-ins.  This causes problems when pstore is executed in
an NMI context through panic() -> kmsg_dump().

This patch changes the mutex to a spin_lock_irqsave then also checks to
see if we are in an NMI context.  If we are in an NMI and can't get the
lock, just print a message stating that and blow by the locking.

All this is probably a hack around the bigger locking problem but it
solves my current situation of trying to sleep in an NMI context.

Tested by loading the lkdtm module and executing a HARDLOCKUP which
will cause the machine to panic inside the nmi handler.

Signed-off-by: Don Zickus <[email protected]>
Acked-by: Matthew Garrett <[email protected]>
Signed-off-by: Tony Luck <[email protected]>
This commit is contained in:
Don Zickus 2011-08-12 10:54:51 -07:00 • committed by Tony Luck
commit abd4d5587b
4 changed files with 24 additions and 10 deletions
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2
drivers/acpi/apei/erst.c
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@ -1165,7 +1165,7 @@ static int __init erst_init(void)
goto err_release_erange;
buf = kmalloc(erst_erange.size, GFP_KERNEL);
mutex_init(&erst_info.buf_mutex);
spin_lock_init(&erst_info.buf_lock);
if (buf) {
erst_info.buf = buf + sizeof(struct cper_pstore_record);
erst_info.bufsize = erst_erange.size -