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authorMarco Elver <elver@google.com>2020-06-24 13:32:46 +0200
committerPeter Zijlstra <peterz@infradead.org>2020-07-10 12:00:00 +0200
commit248591f5d257a19c1cba9ab9da3536bfbc2f0149 (patch)
treea47dc069b160aea78d3fbb9f255c2cff5b3a7942 /kernel/kcsan
parentMerge branch 'tip/x86/entry' (diff)
downloadlinux-248591f5d257a19c1cba9ab9da3536bfbc2f0149.tar.xz
linux-248591f5d257a19c1cba9ab9da3536bfbc2f0149.zip
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@infradead.org> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Ingo Molnar <mingo@kernel.org> Link: https://lkml.kernel.org/r/20200624113246.GA170324@elver.google.com
Diffstat (limited to 'kernel/kcsan')
-rw-r--r--kernel/kcsan/core.c5
-rw-r--r--kernel/kcsan/report.c9
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();