linux-kernel - vmalloc_sync_all(), 64bit kernel, patches 9c48f1c629ecfa114850c03f875c6691003214de, a79e53d85683c6dd9f99c90511028adc2043031f

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Date:	Mon, 26 Nov 2012 15:06:53 -0800
From:	Prasad Koya <prasad.koya@...il.com>
To:	dzickus@...hat.com, aarcange@...hat.com,
	LKML <linux-kernel@...r.kernel.org>
Subject: vmalloc_sync_all(), 64bit kernel, patches 9c48f1c629ecfa114850c03f875c6691003214de,
 a79e53d85683c6dd9f99c90511028adc2043031f

Hi

Before going into crashkernel, nmi_shootdown_cpus() calls
register_die_notifier(), which calls vmalloc_sync_all(). I'm seeing
lockup in sync_global_pgds() (init_64.c). From 3.2 and up,
register_die_notifier() is replaced with register_nmi_handler() (patch
9c48f1c629ecfa114850c03f875c6691003214de), which doesn't call
vmalloc_sync_all(). Is it ok to skip vmalloc_sync_all() in this path?
I see sync_global_pgds() was touched by this patch:
a79e53d85683c6dd9f99c90511028adc2043031f. There are no virtual
machines involved and I see lockups at times.

thank you.
Prasad

/* Halt all other CPUs, calling the specified function on each of them
  *
  * This function can be used to halt all other CPUs on crash
@@ -794,7 +784,8 @@ void nmi_shootdown_cpus(nmi_shootdown_cb callback)

        atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
        /* Would it be better to replace the trap vector here? */
-       if (register_die_notifier(&crash_nmi_nb))
+       if (register_nmi_handler(NMI_LOCAL, crash_nmi_callback,
+                                NMI_FLAG_FIRST, "crash"))
                return;         /* return what? */
--
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