From 248591f5d257a19c1cba9ab9da3536bfbc2f0149 Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Wed, 24 Jun 2020 13:32:46 +0200 Subject: kcsan: Make KCSAN compatible with new IRQ state tracking The new IRQ state tracking code does not honor lockdep_off(), and as such we should again permit tracing by using non-raw functions in core.c. Update the lockdep_off() comment in report.c, to reflect the fact there is still a potential risk of deadlock due to using printk() from scheduler code. Suggested-by: Peter Zijlstra (Intel) Signed-off-by: Marco Elver Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Ingo Molnar Link: https://lkml.kernel.org/r/20200624113246.GA170324@elver.google.com --- kernel/kcsan/core.c | 5 ++--- kernel/kcsan/report.c | 9 +++++---- 2 files changed, 7 insertions(+), 7 deletions(-) diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c index 15f67949d11e..732623c30359 100644 --- a/kernel/kcsan/core.c +++ b/kernel/kcsan/core.c @@ -397,8 +397,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type) } if (!kcsan_interrupt_watcher) - /* Use raw to avoid lockdep recursion via IRQ flags tracing. */ - raw_local_irq_save(irq_flags); + local_irq_save(irq_flags); watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write); if (watchpoint == NULL) { @@ -539,7 +538,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type) kcsan_counter_dec(KCSAN_COUNTER_USED_WATCHPOINTS); out_unlock: if (!kcsan_interrupt_watcher) - raw_local_irq_restore(irq_flags); + local_irq_restore(irq_flags); out: user_access_restore(ua_flags); } diff --git a/kernel/kcsan/report.c b/kernel/kcsan/report.c index ac5f8345bae9..6b2fb1a6d8cd 100644 --- a/kernel/kcsan/report.c +++ b/kernel/kcsan/report.c @@ -606,10 +606,11 @@ void kcsan_report(const volatile void *ptr, size_t size, int access_type, goto out; /* - * With TRACE_IRQFLAGS, lockdep's IRQ trace state becomes corrupted if - * we do not turn off lockdep here; this could happen due to recursion - * into lockdep via KCSAN if we detect a race in utilities used by - * lockdep. + * Because we may generate reports when we're in scheduler code, the use + * of printk() could deadlock. Until such time that all printing code + * called in print_report() is scheduler-safe, accept the risk, and just + * get our message out. As such, also disable lockdep to hide the + * warning, and avoid disabling lockdep for the rest of the kernel. */ lockdep_off(); -- cgit v1.2.3