[tip: x86/entry] x86/debug: Simplify hw_breakpoint_handler()

[tip-bot2 for Peter Zijlstra]

The following commit has been merged into the x86/entry branch of tip:

Commit-ID:     21d44be7b6ff4c254dc971e2c99d4082dd470afd
Gitweb:        https://git.kernel.org/tip/21d44be7b6ff4c254dc971e2c99d4082dd470afd
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Wed, 02 Sep 2020 15:26:00 +02:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Fri, 04 Sep 2020 15:12:56 +02:00

x86/debug: Simplify hw_breakpoint_handler()

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>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Tested-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200902133201.292906672@xxxxxxxxxxxxx

---
 arch/x86/kernel/hw_breakpoint.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c
index ca9de59..7b7d9f2 100644
--- 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 die_args *args)
 		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 die_args *args)
 		 */
 		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 die_args *args)
 	    (dr6 & (~DR_TRAP_BITS)))
 		rc = NOTIFY_DONE;
 
-	put_cpu();
-
 	return rc;
 }