Ryo ONODERA <r...@tetera.org> writes:
> Hi,
>
> Andrew Doran <a...@netbsd.org> writes:
>
>> Hi,
>>
>> This also happened the last time I touched rw_downgrade(), and I backed out
>> the change then, but both times I don't see the bug. I have some questions:
>>
>> - Are you running DIAGNOSTIC and/or LOCKDEBUG? I would be very interested
>> to see what happens with a LOCKDEBUG kernel here.
>
> I will enable LOCKDEBUG and DIAGNOSTIC soon.
Sadly DIAGNOSTIC and LOCKDEBUG with i915drmkms(4) makes my LCD black
and I cannot see any messages.
When i915drmkms is disabled, the kernel boots without freeze in
DIAGNOSTIC and LOCKDEBUG case.
However ioctl(2) to ims(4) causes kernel panic.
I feel that this panic is not related to the boot freeze.
See:
$ crash -M netbsd.10.core -N netbsd.10
Crash version 9.99.39, image version 9.99.39.
System panicked: kernel diagnostic assertion "ci->ci_mtx_count == -1" failed:
file "/usr/src/sys/kern/kern_synch.c", line 676 mi_switch: cpu0: ci_mtx_count
(-2) != -1 (block with spin-mutex held)
Backtrace from time of crash is available.
crash> bt
_KERNEL_OPT_NARCNET() at 0
_KERNEL_OPT_ACPI_SCANPCI() at _KERNEL_OPT_ACPI_SCANPCI
sys_reboot() at sys_reboot
vpanic() at vpanic+0x181
kern_assert() at kern_assert+0x48
mi_switch() at mi_switch+0x9b8
sleepq_block() at sleepq_block+0x1cb
turnstile_block() at turnstile_block+0x5bd
mutex_enter() at mutex_enter+0x31d
iic_acquire_bus() at iic_acquire_bus+0x2a
ihidev_softintr() at ihidev_softintr+0x27
softint_dispatch() at softint_dispatch+0xdb
DDB lost frame for Xsoftintr+0x4f, trying 0xffffda8138ef00f0
Xsoftintr() at Xsoftintr+0x4f
--- interrupt ---
1c6f7f77b9463525:
crash>
>> - Do you have an ATI Radeon graphics chip?
>> - Are you using ZFS?
>
> My GPU is in Intel CPU (KabyLake Refresh).
> And I do not use ZFS at all. All partitions are FFSv2 with WAPBL.
>
>> Thanks,
>> Andrew
>>
>>
>> On Mon, Jan 20, 2020 at 12:41:37PM +0900, Ryo ONODERA wrote:
>>> Hi,
>>>
>>> After this commit, the kernel stalls just before root file system
>>> will be found on my NetBSD/amd64 laptop.
>>>
>>> Reverting
>>> src/sys/kern/kern_rwlock.c to r1.60
>>> and
>>> src/sys/sys/rwlock.h to r1.12
>>> in latest -current tree and I can get the kernel that works like
>>> before.
>>>
>>> And on another laptop, the problematic kernel stalls before root file
>>> system detection like my laptop.
>>>
>>> It may be universal problem.
>>>
>>> Could you take a look at this problem?
>>>
>>> Thank you.
>>>
>>> "Andrew Doran" <a...@netbsd.org> writes:
>>>
>>> > Module Name: src
>>> > Committed By: ad
>>> > Date: Sun Jan 19 18:34:24 UTC 2020
>>> >
>>> > Modified Files:
>>> > src/sys/kern: kern_rwlock.c
>>> > src/sys/sys: rwlock.h
>>> >
>>> > Log Message:
>>> > Tidy rwlocks a bit, no functional change intended. Mainly:
>>> >
>>> > - rw_downgrade(): do it in a for () loop like all the others.
>>> > - Explicitly carry around RW_NODEBUG - don't be lazy.
>>> > - Remove pointless macros.
>>> > - Don't make assertions conditional on LOCKDEBUG, there's no reason.
>>> > - Make space for a new flag bit (not added yet).
>>> >
>>> >
>>> > To generate a diff of this commit:
>>> > cvs rdiff -u -r1.60 -r1.61 src/sys/kern/kern_rwlock.c
>>> > cvs rdiff -u -r1.12 -r1.13 src/sys/sys/rwlock.h
>>> >
>>> > Please note that diffs are not public domain; they are subject to the
>>> > copyright notices on the relevant files.
>>> >
>>> > Modified files:
>>> >
>>> > Index: src/sys/kern/kern_rwlock.c
>>> > diff -u src/sys/kern/kern_rwlock.c:1.60 src/sys/kern/kern_rwlock.c:1.61
>>> > --- src/sys/kern/kern_rwlock.c:1.60 Sun Jan 12 18:37:10 2020
>>> > +++ src/sys/kern/kern_rwlock.c Sun Jan 19 18:34:24 2020
>>> > @@ -1,4 +1,4 @@
>>> > -/* $NetBSD: kern_rwlock.c,v 1.60 2020/01/12 18:37:10 ad Exp $
>>> > */
>>> > +/* $NetBSD: kern_rwlock.c,v 1.61 2020/01/19 18:34:24 ad Exp $
>>> > */
>>> >
>>> > /*-
>>> > * Copyright (c) 2002, 2006, 2007, 2008, 2009, 2019, 2020
>>> > @@ -39,7 +39,9 @@
>>> > */
>>> >
>>> > #include <sys/cdefs.h>
>>> > -__KERNEL_RCSID(0, "$NetBSD: kern_rwlock.c,v 1.60 2020/01/12 18:37:10 ad
>>> > Exp $");
>>> > +__KERNEL_RCSID(0, "$NetBSD: kern_rwlock.c,v 1.61 2020/01/19 18:34:24 ad
>>> > Exp $");
>>> > +
>>> > +#include "opt_lockdebug.h"
>>> >
>>> > #define __RWLOCK_PRIVATE
>>> >
>>> > @@ -63,58 +65,32 @@ __KERNEL_RCSID(0, "$NetBSD: kern_rwlock.
>>> > * LOCKDEBUG
>>> > */
>>> >
>>> > -#if defined(LOCKDEBUG)
>>> > -
>>> > -#define RW_WANTLOCK(rw, op)
>>> > \
>>> > - LOCKDEBUG_WANTLOCK(RW_DEBUG_P(rw), (rw), \
>>> > - (uintptr_t)__builtin_return_address(0), op == RW_READER);
>>> > -#define RW_LOCKED(rw, op)
>>> > \
>>> > - LOCKDEBUG_LOCKED(RW_DEBUG_P(rw), (rw), NULL, \
>>> > - (uintptr_t)__builtin_return_address(0), op == RW_READER);
>>> > -#define RW_UNLOCKED(rw, op)
>>> > \
>>> > - LOCKDEBUG_UNLOCKED(RW_DEBUG_P(rw), (rw), \
>>> > - (uintptr_t)__builtin_return_address(0), op == RW_READER);
>>> > -#define RW_DASSERT(rw, cond)
>>> > \
>>> > -do {
>>> > \
>>> > - if (__predict_false(!(cond))) \
>>> > - rw_abort(__func__, __LINE__, rw, "assertion failed: " #cond);\
>>> > -} while (/* CONSTCOND */ 0);
>>> > -
>>> > -#else /* LOCKDEBUG */
>>> > -
>>> > -#define RW_WANTLOCK(rw, op) /* nothing */
>>> > -#define RW_LOCKED(rw, op) /* nothing */
>>> > -#define RW_UNLOCKED(rw, op) /* nothing */
>>> > -#define RW_DASSERT(rw, cond) /* nothing */
>>> > +#define RW_DEBUG_P(rw) (((rw)->rw_owner & RW_NODEBUG) == 0)
>>> >
>>> > -#endif /* LOCKDEBUG */
>>> > +#define RW_WANTLOCK(rw, op) \
>>> > + LOCKDEBUG_WANTLOCK(RW_DEBUG_P(rw), (rw), \
>>> > + (uintptr_t)__builtin_return_address(0), op == RW_READER);
>>> > +#define RW_LOCKED(rw, op) \
>>> > + LOCKDEBUG_LOCKED(RW_DEBUG_P(rw), (rw), NULL, \
>>> > + (uintptr_t)__builtin_return_address(0), op == RW_READER);
>>> > +#define RW_UNLOCKED(rw, op) \
>>> > + LOCKDEBUG_UNLOCKED(RW_DEBUG_P(rw), (rw), \
>>> > + (uintptr_t)__builtin_return_address(0), op == RW_READER);
>>> >
>>> > /*
>>> > * DIAGNOSTIC
>>> > */
>>> >
>>> > #if defined(DIAGNOSTIC)
>>> > -
>>> > -#define RW_ASSERT(rw, cond)
>>> > \
>>> > -do {
>>> > \
>>> > - if (__predict_false(!(cond))) \
>>> > +#define RW_ASSERT(rw, cond) \
>>> > +do { \
>>> > + if (__predict_false(!(cond))) \
>>> > rw_abort(__func__, __LINE__, rw, "assertion failed: " #cond);\
>>> > } while (/* CONSTCOND */ 0)
>>> > -
>>> > #else
>>> > -
>>> > #define RW_ASSERT(rw, cond) /* nothing */
>>> > -
>>> > #endif /* DIAGNOSTIC */
>>> >
>>> > -#define RW_SETDEBUG(rw, on) ((rw)->rw_owner |= (on) ? 0 :
>>> > RW_NODEBUG)
>>> > -#define RW_DEBUG_P(rw) (((rw)->rw_owner & RW_NODEBUG)
>>> > == 0)
>>> > -#if defined(LOCKDEBUG)
>>> > -#define RW_INHERITDEBUG(n, o) (n) |= (o) & RW_NODEBUG
>>> > -#else /* defined(LOCKDEBUG) */
>>> > -#define RW_INHERITDEBUG(n, o) /* nothing */
>>> > -#endif /* defined(LOCKDEBUG) */
>>> > -
>>> > /*
>>> > * Memory barriers.
>>> > */
>>> > @@ -128,29 +104,6 @@ do {
>>> > \
>>> > #define RW_MEMBAR_PRODUCER() membar_producer()
>>> > #endif
>>> >
>>> > -static void rw_abort(const char *, size_t, krwlock_t *, const char
>>> > *);
>>> > -static void rw_dump(const volatile void *, lockop_printer_t);
>>> > -static lwp_t *rw_owner(wchan_t);
>>> > -
>>> > -static inline uintptr_t
>>> > -rw_cas(krwlock_t *rw, uintptr_t o, uintptr_t n)
>>> > -{
>>> > -
>>> > - RW_INHERITDEBUG(n, o);
>>> > - return (uintptr_t)atomic_cas_ptr((volatile void *)&rw->rw_owner,
>>> > - (void *)o, (void *)n);
>>> > -}
>>> > -
>>> > -static inline void
>>> > -rw_swap(krwlock_t *rw, uintptr_t o, uintptr_t n)
>>> > -{
>>> > -
>>> > - RW_INHERITDEBUG(n, o);
>>> > - n = (uintptr_t)atomic_swap_ptr((volatile void *)&rw->rw_owner,
>>> > - (void *)n);
>>> > - RW_DASSERT(rw, n == o);
>>> > -}
>>> > -
>>> > /*
>>> > * For platforms that do not provide stubs, or for the LOCKDEBUG case.
>>> > */
>>> > @@ -164,6 +117,10 @@ __strong_alias(rw_exit,rw_vector_exit);
>>> > __strong_alias(rw_tryenter,rw_vector_tryenter);
>>> > #endif
>>> >
>>> > +static void rw_abort(const char *, size_t, krwlock_t *, const char
>>> > *);
>>> > +static void rw_dump(const volatile void *, lockop_printer_t);
>>> > +static lwp_t *rw_owner(wchan_t);
>>> > +
>>> > lockops_t rwlock_lockops = {
>>> > .lo_name = "Reader / writer lock",
>>> > .lo_type = LOCKOPS_SLEEP,
>>> > @@ -179,6 +136,37 @@ syncobj_t rw_syncobj = {
>>> > };
>>> >
>>> > /*
>>> > + * rw_cas:
>>> > + *
>>> > + * Do an atomic compare-and-swap on the lock word.
>>> > + */
>>> > +static inline uintptr_t
>>> > +rw_cas(krwlock_t *rw, uintptr_t o, uintptr_t n)
>>> > +{
>>> > +
>>> > + return (uintptr_t)atomic_cas_ptr((volatile void *)&rw->rw_owner,
>>> > + (void *)o, (void *)n);
>>> > +}
>>> > +
>>> > +/*
>>> > + * rw_swap:
>>> > + *
>>> > + * Do an atomic swap of the lock word. This is used only when it's
>>> > + * known that the lock word is set up such that it can't be changed
>>> > + * behind us (assert this), so there's no point considering the
>>> > result.
>>> > + */
>>> > +static inline void
>>> > +rw_swap(krwlock_t *rw, uintptr_t o, uintptr_t n)
>>> > +{
>>> > +
>>> > + n = (uintptr_t)atomic_swap_ptr((volatile void *)&rw->rw_owner,
>>> > + (void *)n);
>>> > +
>>> > + RW_ASSERT(rw, n == o);
>>> > + RW_ASSERT(rw, (o & RW_HAS_WAITERS) != 0);
>>> > +}
>>> > +
>>> > +/*
>>> > * rw_dump:
>>> > *
>>> > * Dump the contents of a rwlock structure.
>>> > @@ -214,16 +202,14 @@ rw_abort(const char *func, size_t line,
>>> > *
>>> > * Initialize a rwlock for use.
>>> > */
>>> > -void _rw_init(krwlock_t *, uintptr_t);
>>> > void
>>> > _rw_init(krwlock_t *rw, uintptr_t return_address)
>>> > {
>>> > - bool dodebug;
>>> >
>>> > - memset(rw, 0, sizeof(*rw));
>>> > -
>>> > - dodebug = LOCKDEBUG_ALLOC(rw, &rwlock_lockops, return_address);
>>> > - RW_SETDEBUG(rw, dodebug);
>>> > + if (LOCKDEBUG_ALLOC(rw, &rwlock_lockops, return_address))
>>> > + rw->rw_owner = 0;
>>> > + else
>>> > + rw->rw_owner = RW_NODEBUG;
>>> > }
>>> >
>>> > void
>>> > @@ -243,7 +229,7 @@ rw_destroy(krwlock_t *rw)
>>> > {
>>> >
>>> > RW_ASSERT(rw, (rw->rw_owner & ~RW_NODEBUG) == 0);
>>> > - LOCKDEBUG_FREE(RW_DEBUG_P(rw), rw);
>>> > + LOCKDEBUG_FREE((rw->rw_owner & RW_NODEBUG) == 0, rw);
>>> > }
>>> >
>>> > /*
>>> > @@ -327,7 +313,7 @@ rw_vector_enter(krwlock_t *rw, const krw
>>> > need_wait = RW_WRITE_LOCKED | RW_WRITE_WANTED;
>>> > queue = TS_READER_Q;
>>> > } else {
>>> > - RW_DASSERT(rw, op == RW_WRITER);
>>> > + RW_ASSERT(rw, op == RW_WRITER);
>>> > incr = curthread | RW_WRITE_LOCKED;
>>> > set_wait = RW_HAS_WAITERS | RW_WRITE_WANTED;
>>> > need_wait = RW_WRITE_LOCKED | RW_THREAD;
>>> > @@ -430,7 +416,7 @@ rw_vector_enter(krwlock_t *rw, const krw
>>> > (uintptr_t)__builtin_return_address(0)));
>>> > LOCKSTAT_EXIT(lsflag);
>>> >
>>> > - RW_DASSERT(rw, (op != RW_READER && RW_OWNER(rw) == curthread) ||
>>> > + RW_ASSERT(rw, (op != RW_READER && RW_OWNER(rw) == curthread) ||
>>> > (op == RW_READER && RW_COUNT(rw) != 0));
>>> > RW_LOCKED(rw, op);
>>> > }
>>> > @@ -448,7 +434,8 @@ rw_vector_exit(krwlock_t *rw)
>>> > int rcnt, wcnt;
>>> > lwp_t *l;
>>> >
>>> > - curthread = (uintptr_t)curlwp;
>>> > + l = curlwp;
>>> > + curthread = (uintptr_t)l;
>>> > RW_ASSERT(rw, curthread != 0);
>>> >
>>> > /*
>>> > @@ -491,8 +478,8 @@ rw_vector_exit(krwlock_t *rw)
>>> > */
>>> > ts = turnstile_lookup(rw);
>>> > owner = rw->rw_owner;
>>> > - RW_DASSERT(rw, ts != NULL);
>>> > - RW_DASSERT(rw, (owner & RW_HAS_WAITERS) != 0);
>>> > + RW_ASSERT(rw, ts != NULL);
>>> > + RW_ASSERT(rw, (owner & RW_HAS_WAITERS) != 0);
>>> >
>>> > wcnt = TS_WAITERS(ts, TS_WRITER_Q);
>>> > rcnt = TS_WAITERS(ts, TS_READER_Q);
>>> > @@ -509,31 +496,35 @@ rw_vector_exit(krwlock_t *rw)
>>> > * do the work of acquiring the lock in rw_vector_enter().
>>> > */
>>> > if (rcnt == 0 || decr == RW_READ_INCR) {
>>> > - RW_DASSERT(rw, wcnt != 0);
>>> > - RW_DASSERT(rw, (owner & RW_WRITE_WANTED) != 0);
>>> > + RW_ASSERT(rw, wcnt != 0);
>>> > + RW_ASSERT(rw, (owner & RW_WRITE_WANTED) != 0);
>>> >
>>> > if (rcnt != 0) {
>>> > /* Give the lock to the longest waiting writer. */
>>> > l = TS_FIRST(ts, TS_WRITER_Q);
>>> > - newown = (uintptr_t)l | RW_WRITE_LOCKED |
>>> > RW_HAS_WAITERS;
>>> > + newown = (uintptr_t)l | (owner & RW_NODEBUG);
>>> > + newown |= RW_WRITE_LOCKED | RW_HAS_WAITERS;
>>> > if (wcnt > 1)
>>> > newown |= RW_WRITE_WANTED;
>>> > rw_swap(rw, owner, newown);
>>> > turnstile_wakeup(ts, TS_WRITER_Q, 1, l);
>>> > } else {
>>> > /* Wake all writers and let them fight it out. */
>>> > - rw_swap(rw, owner, RW_WRITE_WANTED);
>>> > + newown = owner & RW_NODEBUG;
>>> > + newown |= RW_WRITE_WANTED;
>>> > + rw_swap(rw, owner, newown);
>>> > turnstile_wakeup(ts, TS_WRITER_Q, wcnt, NULL);
>>> > }
>>> > } else {
>>> > - RW_DASSERT(rw, rcnt != 0);
>>> > + RW_ASSERT(rw, rcnt != 0);
>>> >
>>> > /*
>>> > * Give the lock to all blocked readers. If there
>>> > * is a writer waiting, new readers that arrive
>>> > * after the release will be blocked out.
>>> > */
>>> > - newown = rcnt << RW_READ_COUNT_SHIFT;
>>> > + newown = owner & RW_NODEBUG;
>>> > + newown += rcnt << RW_READ_COUNT_SHIFT;
>>> > if (wcnt != 0)
>>> > newown |= RW_HAS_WAITERS | RW_WRITE_WANTED;
>>> >
>>> > @@ -552,8 +543,10 @@ int
>>> > rw_vector_tryenter(krwlock_t *rw, const krw_t op)
>>> > {
>>> > uintptr_t curthread, owner, incr, need_wait, next;
>>> > + lwp_t *l;
>>> >
>>> > - curthread = (uintptr_t)curlwp;
>>> > + l = curlwp;
>>> > + curthread = (uintptr_t)l;
>>> >
>>> > RW_ASSERT(rw, curthread != 0);
>>> >
>>> > @@ -561,7 +554,7 @@ rw_vector_tryenter(krwlock_t *rw, const
>>> > incr = RW_READ_INCR;
>>> > need_wait = RW_WRITE_LOCKED | RW_WRITE_WANTED;
>>> > } else {
>>> > - RW_DASSERT(rw, op == RW_WRITER);
>>> > + RW_ASSERT(rw, op == RW_WRITER);
>>> > incr = curthread | RW_WRITE_LOCKED;
>>> > need_wait = RW_WRITE_LOCKED | RW_THREAD;
>>> > }
>>> > @@ -572,24 +565,23 @@ rw_vector_tryenter(krwlock_t *rw, const
>>> > next = rw_cas(rw, owner, owner + incr);
>>> > if (__predict_true(next == owner)) {
>>> > /* Got it! */
>>> > - RW_MEMBAR_ENTER();
>>> > break;
>>> > }
>>> > }
>>> >
>>> > RW_WANTLOCK(rw, op);
>>> > RW_LOCKED(rw, op);
>>> > - RW_DASSERT(rw, (op != RW_READER && RW_OWNER(rw) == curthread) ||
>>> > + RW_ASSERT(rw, (op != RW_READER && RW_OWNER(rw) == curthread) ||
>>> > (op == RW_READER && RW_COUNT(rw) != 0));
>>> >
>>> > + RW_MEMBAR_ENTER();
>>> > return 1;
>>> > }
>>> >
>>> > /*
>>> > * rw_downgrade:
>>> > *
>>> > - * Downgrade a write lock to a read lock. Optimise memory
>>> > accesses for
>>> > - * the uncontended case.
>>> > + * Downgrade a write lock to a read lock.
>>> > */
>>> > void
>>> > rw_downgrade(krwlock_t *rw)
>>> > @@ -597,55 +589,64 @@ rw_downgrade(krwlock_t *rw)
>>> > uintptr_t owner, curthread, newown, next;
>>> > turnstile_t *ts;
>>> > int rcnt, wcnt;
>>> > + lwp_t *l;
>>> >
>>> > - curthread = (uintptr_t)curlwp;
>>> > + l = curlwp;
>>> > + curthread = (uintptr_t)l;
>>> > RW_ASSERT(rw, curthread != 0);
>>> > - RW_DASSERT(rw, (rw->rw_owner & RW_WRITE_LOCKED) != 0);
>>> > + RW_ASSERT(rw, (rw->rw_owner & RW_WRITE_LOCKED) != 0);
>>> > RW_ASSERT(rw, RW_OWNER(rw) == curthread);
>>> > RW_UNLOCKED(rw, RW_WRITER);
>>> > #if !defined(DIAGNOSTIC)
>>> > __USE(curthread);
>>> > #endif
>>> >
>>> > - /*
>>> > - * If there are no waiters, so we can do this the easy way.
>>> > - * Try swapping us down to one read hold. If it fails, the
>>> > - * lock condition has changed and we most likely now have
>>> > - * waiters.
>>> > - */
>>> > RW_MEMBAR_PRODUCER();
>>> > - owner = curthread | RW_WRITE_LOCKED;
>>> > - next = rw_cas(rw, owner, RW_READ_INCR);
>>> > - if (__predict_true(next == owner)) {
>>> > - RW_LOCKED(rw, RW_READER);
>>> > - RW_DASSERT(rw, (rw->rw_owner & RW_WRITE_LOCKED) == 0);
>>> > - RW_DASSERT(rw, RW_COUNT(rw) != 0);
>>> > - return;
>>> > - }
>>> >
>>> > - /*
>>> > - * Grab the turnstile chain lock. This gets the interlock
>>> > - * on the sleep queue. Once we have that, we can adjust the
>>> > - * waiter bits.
>>> > - */
>>> > - for (;;) {
>>> > - owner = next;
>>> > + for (owner = rw->rw_owner;; owner = next) {
>>> > + /*
>>> > + * If there are no waiters we can do this the easy way. Try
>>> > + * swapping us down to one read hold. If it fails, the lock
>>> > + * condition has changed and we most likely now have
>>> > + * waiters.
>>> > + */
>>> > + if ((owner & RW_HAS_WAITERS) == 0) {
>>> > + newown = (owner & RW_NODEBUG);
>>> > + next = rw_cas(rw, owner, newown + RW_READ_INCR);
>>> > + if (__predict_true(next == owner)) {
>>> > + RW_LOCKED(rw, RW_READER);
>>> > + RW_ASSERT(rw,
>>> > + (rw->rw_owner & RW_WRITE_LOCKED) == 0);
>>> > + RW_ASSERT(rw, RW_COUNT(rw) != 0);
>>> > + return;
>>> > + }
>>> > + continue;
>>> > + }
>>> > +
>>> > + /*
>>> > + * Grab the turnstile chain lock. This gets the interlock
>>> > + * on the sleep queue. Once we have that, we can adjust the
>>> > + * waiter bits.
>>> > + */
>>> > ts = turnstile_lookup(rw);
>>> > - RW_DASSERT(rw, ts != NULL);
>>> > + RW_ASSERT(rw, ts != NULL);
>>> >
>>> > rcnt = TS_WAITERS(ts, TS_READER_Q);
>>> > wcnt = TS_WAITERS(ts, TS_WRITER_Q);
>>> >
>>> > - /*
>>> > - * If there are no readers, just preserve the waiters
>>> > - * bits, swap us down to one read hold and return.
>>> > - */
>>> > if (rcnt == 0) {
>>> > - RW_DASSERT(rw, wcnt != 0);
>>> > - RW_DASSERT(rw, (rw->rw_owner & RW_WRITE_WANTED) != 0);
>>> > - RW_DASSERT(rw, (rw->rw_owner & RW_HAS_WAITERS) != 0);
>>> > -
>>> > - newown = RW_READ_INCR | RW_HAS_WAITERS |
>>> > RW_WRITE_WANTED;
>>> > + /*
>>> > + * If there are no readers, just preserve the
>>> > + * waiters bits, swap us down to one read hold and
>>> > + * return.
>>> > + */
>>> > + RW_ASSERT(rw, wcnt != 0);
>>> > + RW_ASSERT(rw, (rw->rw_owner & RW_WRITE_WANTED) != 0);
>>> > + RW_ASSERT(rw, (rw->rw_owner & RW_HAS_WAITERS) != 0);
>>> > +
>>> > + newown = owner & RW_NODEBUG;
>>> > + newown = RW_READ_INCR | RW_HAS_WAITERS |
>>> > + RW_WRITE_WANTED;
>>> > next = rw_cas(rw, owner, newown);
>>> > turnstile_exit(rw);
>>> > if (__predict_true(next == owner))
>>> > @@ -653,11 +654,12 @@ rw_downgrade(krwlock_t *rw)
>>> > } else {
>>> > /*
>>> > * Give the lock to all blocked readers. We may
>>> > - * retain one read hold if downgrading. If there
>>> > - * is a writer waiting, new readers will be blocked
>>> > + * retain one read hold if downgrading. If there is
>>> > + * a writer waiting, new readers will be blocked
>>> > * out.
>>> > */
>>> > - newown = (rcnt << RW_READ_COUNT_SHIFT) + RW_READ_INCR;
>>> > + newown = owner & RW_NODEBUG;
>>> > + newown += (rcnt << RW_READ_COUNT_SHIFT) + RW_READ_INCR;
>>> > if (wcnt != 0)
>>> > newown |= RW_HAS_WAITERS | RW_WRITE_WANTED;
>>> >
>>> > @@ -673,22 +675,24 @@ rw_downgrade(krwlock_t *rw)
>>> >
>>> > RW_WANTLOCK(rw, RW_READER);
>>> > RW_LOCKED(rw, RW_READER);
>>> > - RW_DASSERT(rw, (rw->rw_owner & RW_WRITE_LOCKED) == 0);
>>> > - RW_DASSERT(rw, RW_COUNT(rw) != 0);
>>> > + RW_ASSERT(rw, (rw->rw_owner & RW_WRITE_LOCKED) == 0);
>>> > + RW_ASSERT(rw, RW_COUNT(rw) != 0);
>>> > }
>>> >
>>> > /*
>>> > * rw_tryupgrade:
>>> > *
>>> > * Try to upgrade a read lock to a write lock. We must be the only
>>> > - * reader. Optimise memory accesses for the uncontended case.
>>> > + * reader.
>>> > */
>>> > int
>>> > rw_tryupgrade(krwlock_t *rw)
>>> > {
>>> > uintptr_t owner, curthread, newown, next;
>>> > + struct lwp *l;
>>> >
>>> > - curthread = (uintptr_t)curlwp;
>>> > + l = curlwp;
>>> > + curthread = (uintptr_t)l;
>>> > RW_ASSERT(rw, curthread != 0);
>>> > RW_ASSERT(rw, rw_read_held(rw));
>>> >
>>> > @@ -709,8 +713,8 @@ rw_tryupgrade(krwlock_t *rw)
>>> > RW_UNLOCKED(rw, RW_READER);
>>> > RW_WANTLOCK(rw, RW_WRITER);
>>> > RW_LOCKED(rw, RW_WRITER);
>>> > - RW_DASSERT(rw, rw->rw_owner & RW_WRITE_LOCKED);
>>> > - RW_DASSERT(rw, RW_OWNER(rw) == curthread);
>>> > + RW_ASSERT(rw, rw->rw_owner & RW_WRITE_LOCKED);
>>> > + RW_ASSERT(rw, RW_OWNER(rw) == curthread);
>>> >
>>> > return 1;
>>> > }
>>> >
>>> > Index: src/sys/sys/rwlock.h
>>> > diff -u src/sys/sys/rwlock.h:1.12 src/sys/sys/rwlock.h:1.13
>>> > --- src/sys/sys/rwlock.h:1.12 Wed Jan 1 21:34:39 2020
>>> > +++ src/sys/sys/rwlock.h Sun Jan 19 18:34:24 2020
>>> > @@ -1,7 +1,7 @@
>>> > -/* $NetBSD: rwlock.h,v 1.12 2020/01/01 21:34:39 ad Exp $ */
>>> > +/* $NetBSD: rwlock.h,v 1.13 2020/01/19 18:34:24 ad Exp $ */
>>> >
>>> > /*-
>>> > - * Copyright (c) 2002, 2006, 2007, 2008, 2019 The NetBSD Foundation, Inc.
>>> > + * Copyright (c) 2002, 2006, 2007, 2008, 2019, 2020 The NetBSD
>>> > Foundation, Inc.
>>> > * All rights reserved.
>>> > *
>>> > * This code is derived from software contributed to The NetBSD
>>> > Foundation
>>> > @@ -45,10 +45,6 @@
>>> > * rw_tryenter()
>>> > */
>>> >
>>> > -#if defined(_KERNEL_OPT)
>>> > -#include "opt_lockdebug.h"
>>> > -#endif
>>> > -
>>> > #if !defined(_KERNEL)
>>> > #include <sys/types.h>
>>> > #include <sys/inttypes.h>
>>> > @@ -75,13 +71,9 @@ typedef struct krwlock krwlock_t;
>>> > #define RW_HAS_WAITERS 0x01UL /* lock has waiters */
>>> > #define RW_WRITE_WANTED 0x02UL /* >= 1 waiter is a writer */
>>> > #define RW_WRITE_LOCKED 0x04UL /* lock is currently write
>>> > locked */
>>> > -#if defined(LOCKDEBUG)
>>> > -#define RW_NODEBUG 0x08UL /* LOCKDEBUG disabled */
>>> > -#else
>>> > -#define RW_NODEBUG 0x00UL /* do nothing */
>>> > -#endif /* LOCKDEBUG */
>>> > +#define RW_NODEBUG 0x10UL /* LOCKDEBUG disabled */
>>> >
>>> > -#define RW_READ_COUNT_SHIFT 4
>>> > +#define RW_READ_COUNT_SHIFT 5
>>> > #define RW_READ_INCR (1UL << RW_READ_COUNT_SHIFT)
>>> > #define RW_THREAD ((uintptr_t)-RW_READ_INCR)
>>> > #define RW_OWNER(rw) ((rw)->rw_owner & RW_THREAD)
>>> > @@ -91,6 +83,7 @@ typedef struct krwlock krwlock_t;
>>> > void rw_vector_enter(krwlock_t *, const krw_t);
>>> > void rw_vector_exit(krwlock_t *);
>>> > int rw_vector_tryenter(krwlock_t *, const krw_t);
>>> > +void _rw_init(krwlock_t *, uintptr_t);
>>> > #endif /* __RWLOCK_PRIVATE */
>>> >
>>> > struct krwlock {
>>> >
>>>
>>> --
>>> Ryo ONODERA // r...@tetera.org
>>> PGP fingerprint = 82A2 DC91 76E0 A10A 8ABB FD1B F404 27FA C7D1 15F3
>
> --
> Ryo ONODERA // r...@tetera.org
> PGP fingerprint = 82A2 DC91 76E0 A10A 8ABB FD1B F404 27FA C7D1 15F3
--
Ryo ONODERA // r...@tetera.org
PGP fingerprint = 82A2 DC91 76E0 A10A 8ABB FD1B F404 27FA C7D1 15F3
