[patch 2/3] Use per-cpu elf_prstatus

[Simon Horman]

Use a pre-allocated per-cpu variable for saving the cpu registers, as per
the IA64 specific code. This is in order to reduce possible stack
contention at crash-time as per the inline comment.

A following patch will update ia64 to use crash_save_cpu() rather
than its own re-implementation of the routine.

Signed-off-by: Simon Horman <[EMAIL PROTECTED]>

--- 
 linux-2.6/kernel/kexec.c |   20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

Index: linux-2.6/kernel/kexec.c
===================================================================
--- linux-2.6.orig/kernel/kexec.c       2007-05-08 18:08:50.000000000 +0900
+++ linux-2.6/kernel/kexec.c    2007-05-08 18:22:45.000000000 +0900
@@ -1097,9 +1097,18 @@ static void final_note(u32 *buf)
        memcpy(buf, &note, sizeof(note));
 }
 
+/*
+ * There is some concern that on architectures where struct elf_prstatus is
+ * large, such as IA64, having elf_prstatus on the stack in
+ * crash_save_cpu() could cause problems given that this function
+ * is run after a kernel crash has occured. To aleviate this problem
+ * a pre-allocated per-cpu value is used instead.
+ */
+static DEFINE_PER_CPU(struct elf_prstatus, elf_prstatus);
+
 void crash_save_cpu(struct pt_regs *regs, int cpu)
 {
-       struct elf_prstatus prstatus;
+       struct elf_prstatus *prstatus;
        u32 *buf;
 
        if ((cpu < 0) || (cpu >= NR_CPUS))
@@ -1115,11 +1124,12 @@ void crash_save_cpu(struct pt_regs *regs
        buf = (u32*)per_cpu_ptr(crash_notes, cpu);
        if (!buf)
                return;
-       memset(&prstatus, 0, sizeof(prstatus));
-       prstatus.pr_pid = current->pid;
-       kexec_elf_core_copy_regs(&prstatus.pr_reg, regs);
+       prstatus = &per_cpu(elf_prstatus, cpu);
+       memset(prstatus, 0, sizeof(struct elf_prstatus));
+       prstatus->pr_pid = current->pid;
+       kexec_elf_core_copy_regs(&(prstatus->pr_reg), regs);
        buf = append_elf_note(buf, KEXEC_CORE_NOTE_NAME, NT_PRSTATUS,
-                             &prstatus, sizeof(prstatus));
+                             prstatus, sizeof(struct elf_prstatus));
        final_note(buf);
 }
 

-- 

-- 
Horms
  H: http://www.vergenet.net/~horms/
  W: http://www.valinux.co.jp/en/

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