This is a note to let you know that I've just added the patch titled
powerpc: Fix hcall tracepoint recursion
to the 2.6.37-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-fix-hcall-tracepoint-recursion.patch
and it can be found in the queue-2.6.37 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 57cdfdf829a850a317425ed93c6a576c9ee6329c Mon Sep 17 00:00:00 2001
From: Anton Blanchard <[email protected]>
Date: Thu, 21 Oct 2010 00:52:12 +0000
Subject: powerpc: Fix hcall tracepoint recursion
From: Anton Blanchard <[email protected]>
commit 57cdfdf829a850a317425ed93c6a576c9ee6329c upstream.
Spinlocks on shared processor partitions use H_YIELD to notify the
hypervisor we are waiting on another virtual CPU. Unfortunately this means
the hcall tracepoints can recurse.
The patch below adds a percpu depth and checks it on both the entry and
exit hcall tracepoints.
Signed-off-by: Anton Blanchard <[email protected]>
Acked-by: Steven Rostedt <[email protected]>
Signed-off-by: Benjamin Herrenschmidt <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
arch/powerpc/platforms/pseries/lpar.c | 37 ++++++++++++++++++++++++++++++++++
1 file changed, 37 insertions(+)
--- a/arch/powerpc/platforms/pseries/lpar.c
+++ b/arch/powerpc/platforms/pseries/lpar.c
@@ -701,6 +701,13 @@ EXPORT_SYMBOL(arch_free_page);
/* NB: reg/unreg are called while guarded with the tracepoints_mutex */
extern long hcall_tracepoint_refcount;
+/*
+ * Since the tracing code might execute hcalls we need to guard against
+ * recursion. One example of this are spinlocks calling H_YIELD on
+ * shared processor partitions.
+ */
+static DEFINE_PER_CPU(unsigned int, hcall_trace_depth);
+
void hcall_tracepoint_regfunc(void)
{
hcall_tracepoint_refcount++;
@@ -713,12 +720,42 @@ void hcall_tracepoint_unregfunc(void)
void __trace_hcall_entry(unsigned long opcode, unsigned long *args)
{
+ unsigned long flags;
+ unsigned int *depth;
+
+ local_irq_save(flags);
+
+ depth = &__get_cpu_var(hcall_trace_depth);
+
+ if (*depth)
+ goto out;
+
+ (*depth)++;
trace_hcall_entry(opcode, args);
+ (*depth)--;
+
+out:
+ local_irq_restore(flags);
}
void __trace_hcall_exit(long opcode, unsigned long retval,
unsigned long *retbuf)
{
+ unsigned long flags;
+ unsigned int *depth;
+
+ local_irq_save(flags);
+
+ depth = &__get_cpu_var(hcall_trace_depth);
+
+ if (*depth)
+ goto out;
+
+ (*depth)++;
trace_hcall_exit(opcode, retval, retbuf);
+ (*depth)--;
+
+out:
+ local_irq_restore(flags);
}
#endif
Patches currently in stable-queue which might be from [email protected] are
queue-2.6.37/powerpc-numa-fix-bug-in-unmap_cpu_from_node.patch
queue-2.6.37/powerpc-fix-hcall-tracepoint-recursion.patch
_______________________________________________
stable mailing list
[email protected]
http://linux.kernel.org/mailman/listinfo/stable
