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authorAnton Blanchard <anton@samba.org>2010-10-21 00:52:12 +0000
committerGreg Kroah-Hartman <gregkh@suse.de>2011-03-21 12:44:56 -0700
commit4c0821e7a7ebca3614995845b91a640c6919fdc5 (patch)
treed5c6b2271858199b0bb9fd537714a27a9b91dfd1 /arch
parent1f9b4d210cc74010c9b6f24dc854bf1da52262f8 (diff)
powerpc: Fix hcall tracepoint recursion
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 <anton@samba.org> Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'arch')
-rw-r--r--arch/powerpc/platforms/pseries/lpar.c37
1 files changed, 37 insertions, 0 deletions
diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c
index 0707653612ba..2e20b8d82944 100644
--- a/arch/powerpc/platforms/pseries/lpar.c
+++ b/arch/powerpc/platforms/pseries/lpar.c
@@ -673,6 +673,13 @@ 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++;
@@ -685,12 +692,42 @@ 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