From: Rohan McLure rmclure@linux.ibm.com
[ Upstream commit 2a7ce82dc46c591c9244057d89a6591c9639b9b9 ]
In order for KCSAN to increase its likelihood of observing a data race, it sets a watchpoint on memory accesses and stalls, allowing for detection of conflicting accesses by other kernel threads or interrupts.
Stalls are implemented by injecting a call to udelay in instrumented code. To prevent recursive instrumentation, exclude udelay from being instrumented.
Signed-off-by: Rohan McLure rmclure@linux.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20230206021801.105268-3-rmclure@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/kernel/time.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 1d20f0f77a920..ba9b54d35f570 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -436,7 +436,7 @@ void vtime_flush(struct task_struct *tsk) #define calc_cputime_factors() #endif
-void __delay(unsigned long loops) +void __no_kcsan __delay(unsigned long loops) { unsigned long start;
@@ -457,7 +457,7 @@ void __delay(unsigned long loops) } EXPORT_SYMBOL(__delay);
-void udelay(unsigned long usecs) +void __no_kcsan udelay(unsigned long usecs) { __delay(tb_ticks_per_usec * usecs); }