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kcsan: Make KCSAN compatible with new IRQ state tracking

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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
This commit is contained in:
Marco Elver 2020-06-24 13:32:46 +02:00 committed by Peter Zijlstra
parent e1bcad609f
commit 248591f5d2
2 changed files with 7 additions and 7 deletions
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5
kernel/kcsan/core.c
View File

@ -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);
}

9
kernel/kcsan/report.c
View File

@ -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();