On 2017 Dec 14 (Thu) at 12:23:00 +0100 (+0100), Martin Pieuchot wrote:
:On 14/12/17(Thu) 12:03, Peter Hessler wrote:
:> This is the normal arm64 "pmap bug" panic.
:
:Thanks Peter, the diff below should fix the two problems present in your
:trace:
:
:> ddb> show panic
:> uvm_fault failed: ffffff80002619b4
:
:I love that arm64 is doing the right thing and call panic(9) for UVM
:faults.
:
:> ddb> bo re
:> panic: mtx 0xffffff8000928138: locking against myself
:
:This happens when faulting/panic'ing with a mutex held. The diff below
:contains the same trick I added for rwlock, close the eyes and try
:harder.
:
:Note that the mutex part of the diff below is only for ARM64, I'll
:generalize it if we reach a consensus.
:
:> ddb> # holding down enter, repeats last command 'bo re'
:> panic: netlock: lock not held
:> Stopped at panic+0x154: db_enter() at panic+0x150
:> panic() at if_downall+0x74
:> if_downall() at boot+0x68
:
:This is new to me. My previous fix for rwlock() did not include a check
:for the slow path of rw_exit_write(9)! Diff below should fix that.
:
:
This reads fine to me. While I haven't triggered a panic on arm64 yet, I
think it should go in.
OK
:Index: kern/kern_rwlock.c
:===================================================================
:RCS file: /cvs/src/sys/kern/kern_rwlock.c,v
:retrieving revision 1.32
:diff -u -p -r1.32 kern_rwlock.c
:--- kern/kern_rwlock.c 24 Oct 2017 08:53:15 -0000 1.32
:+++ kern/kern_rwlock.c 14 Dec 2017 11:16:29 -0000
:@@ -287,6 +287,10 @@ _rw_exit(struct rwlock *rwl LOCK_FL_VARS
: int wrlock = owner & RWLOCK_WRLOCK;
: unsigned long set;
:
:+ /* Avoid deadlocks after panic */
:+ if (panicstr)
:+ return;
:+
: if (wrlock)
: rw_assert_wrlock(rwl);
: else
:Index: arch/arm64/arm64/arm64_mutex.c
:===================================================================
:RCS file: /cvs/src/sys/arch/arm64/arm64/arm64_mutex.c,v
:retrieving revision 1.2
:diff -u -p -r1.2 arm64_mutex.c
:--- arch/arm64/arm64/arm64_mutex.c 30 Apr 2017 16:45:45 -0000 1.2
:+++ arch/arm64/arm64/arm64_mutex.c 14 Dec 2017 11:13:57 -0000
:@@ -57,6 +57,10 @@ mtx_enter(struct mutex *mtx)
: int ticks = __mp_lock_spinout;
: #endif
:
:+ /* Avoid deadlocks after panic */
:+ if (panicstr)
:+ return;
:+
: while (mtx_enter_try(mtx) == 0) {
: #ifdef MP_LOCKDEBUG
: if (--ticks == 0) {
:@@ -73,7 +77,7 @@ mtx_enter_try(struct mutex *mtx)
: {
: struct cpu_info *owner, *ci = curcpu();
: int s;
:-
:+
: if (mtx->mtx_wantipl != IPL_NONE)
: s = splraise(mtx->mtx_wantipl);
:
:@@ -102,6 +106,10 @@ void
: mtx_leave(struct mutex *mtx)
: {
: int s;
:+
:+ /* Avoid deadlocks after panic */
:+ if (panicstr)
:+ return;
:
: MUTEX_ASSERT_LOCKED(mtx);
:
:
--
In those days he was wiser than he is now -- he used to frequently take
my advice.
-- Winston Churchill
