[4.4-stable 15/22] perf/x86: Shut up false-positive -Wmaybe-uninitialized warning

[Arnd Bergmann]

commit 11d8b05855f3749bcb6c57e2c4052921b9605c77 upstream.

The intialization function checks for various failure scenarios, but
unfortunately the compiler gets a little confused about the possible
combinations, leading to a false-positive build warning when
-Wmaybe-uninitialized is set:

  arch/x86/events/core.c: In function âinit_hw_perf_eventsâ:
  arch/x86/events/core.c:264:3: warning: âreg_failâ may be used uninitialized in this function [-Wmaybe-uninitialized]
  arch/x86/events/core.c:264:3: warning: âval_failâ may be used uninitialized in this function [-Wmaybe-uninitialized]
     pr_err(FW_BUG "the BIOS has corrupted hw-PMU resources (MSR %x is %Lx)\n",

We can't actually run into this case, so this shuts up the warning
by initializing the variables to a known-invalid state.

Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20170719125310.2487451-2-arnd@xxxxxxxx
Link: https://patchwork.kernel.org/patch/9392595/
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
[arnd: rebased to 4.4]
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
 arch/x86/kernel/cpu/perf_event.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 5b2f2306fbcc..b52a8d08ab36 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -188,8 +188,8 @@ static void release_pmc_hardware(void) {}
 
 static bool check_hw_exists(void)
 {
-	u64 val, val_fail, val_new= ~0;
-	int i, reg, reg_fail, ret = 0;
+	u64 val, val_fail = -1, val_new= ~0;
+	int i, reg, reg_fail = -1, ret = 0;
 	int bios_fail = 0;
 	int reg_safe = -1;
 
-- 
2.9.0