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Commit 57cdfdf8 authored by Anton Blanchard's avatar Anton Blanchard Committed by Benjamin Herrenschmidt
Browse files

powerpc: Fix hcall tracepoint recursion 



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: default avatarAnton Blanchard <anton@samba.org>
Acked-by: default avatarSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
CC: stable@kernel.org
parent 429f4d8d

arch/powerpc/platforms/pseries/lpar.c

+37 −0
Original line number Diff line number Diff line
@@ -713,6 +713,13 @@ 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++;
@@ -725,12 +732,42 @@ 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