2.6.37-stable review patch. If anyone has any objections, please let us know.
------------------ 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 _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
