[PATCH 11/13] x86/debug: Simplify hw_breakpoint_handler()

From: Peter Zijlstra
Date: Wed Sep 02 2020 - 09:57:44 EST


This is called with interrupts disabled, there's no point in using
get_cpu() and per_cpu().

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
arch/x86/kernel/hw_breakpoint.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)

--- a/arch/x86/kernel/hw_breakpoint.c
+++ b/arch/x86/kernel/hw_breakpoint.c
@@ -487,7 +487,7 @@ EXPORT_SYMBOL_GPL(hw_breakpoint_restore)
*/
static int hw_breakpoint_handler(struct die_args *args)
{
- int i, cpu, rc = NOTIFY_STOP;
+ int i, rc = NOTIFY_STOP;
struct perf_event *bp;
unsigned long dr6;
unsigned long *dr6_p;
@@ -505,12 +505,10 @@ static int hw_breakpoint_handler(struct
return NOTIFY_DONE;

/*
- * Assert that local interrupts are disabled
* Reset the DRn bits in the virtualized register value.
* The ptrace trigger routine will add in whatever is needed.
*/
current->thread.debugreg6 &= ~DR_TRAP_BITS;
- cpu = get_cpu();

/* Handle all the breakpoints that were triggered */
for (i = 0; i < HBP_NUM; ++i) {
@@ -525,7 +523,7 @@ static int hw_breakpoint_handler(struct
*/
rcu_read_lock();

- bp = per_cpu(bp_per_reg[i], cpu);
+ bp = this_cpu_read(bp_per_reg[i]);
/*
* Reset the 'i'th TRAP bit in dr6 to denote completion of
* exception handling
@@ -560,8 +558,6 @@ static int hw_breakpoint_handler(struct
(dr6 & (~DR_TRAP_BITS)))
rc = NOTIFY_DONE;

- put_cpu();
-
return rc;
}