The following commit has been merged into the locking/core branch of tip:
Commit-ID: 248591f5d257a19c1cba9ab9da3536bfbc2f0149
Gitweb: https://git.kernel.org/tip/248591f5d257a19c1cba9ab9da3536bfbc2f0149
Author: Marco Elver <elver@xxxxxxxxxx>
AuthorDate: Wed, 24 Jun 2020 13:32:46 +02:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Fri, 10 Jul 2020 12:00:00 +02:00
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) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Ingo Molnar <mingo@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200624113246.GA170324@xxxxxxxxxxxxxxxx
---
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 15f6794..732623c 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 ac5f834..6b2fb1a 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();
|