| Date | Tue, 15 Feb 2011 16:21:35 -0800 | From | Greg KH <> | Subject | [patch 127/176] powerpc: Fix hcall tracepoint recursion |
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2.6.36-stable review patch. If anyone has any objections, please let us know.
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From: Anton Blanchard <anton@samba.org>
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>
--- 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 @@ -680,6 +680,13 @@ 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++; @@ -692,12 +699,42 @@ 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
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