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powerpc: Fix hcall tracepoint recursion

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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>
CC: stable@kernel.org
This commit is contained in:
Anton Blanchard 2010-10-21 00:52:12 +00:00 committed by Benjamin Herrenschmidt
parent 429f4d8d20
commit 57cdfdf829
1 changed files with 37 additions and 0 deletions
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37
arch/powerpc/platforms/pseries/lpar.c
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@ -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