In message <CAGudoHFbuUgCrBa1JS6S5ynB_obpwBJdyRP66bd-WuhHO8ZP7A@mail.gmail.c
om>
, Mateusz Guzik writes:
> Can you show:
>
> sysctl vm.phys_segso

vm.phys_segs: 
SEGMENT 0:

start:     0x10000
end:       0x9d000
domain:    0
free list: 0xffffffff80f31070

SEGMENT 1:

start:     0x100000
end:       0x1000000
domain:    0
free list: 0xffffffff80f31070

SEGMENT 2:

start:     0x1000000
end:       0x1ca4000
domain:    0
free list: 0xffffffff80f30e00

SEGMENT 3:

start:     0x1cb3000
end:       0x1ce3000
domain:    0
free list: 0xffffffff80f30e00

SEGMENT 4:

start:     0x1f00000
end:       0x20000000
domain:    0
free list: 0xffffffff80f30e00

SEGMENT 5:

start:     0x20200000
end:       0x40000000
domain:    0
free list: 0xffffffff80f30e00

SEGMENT 6:

start:     0x40203000
end:       0xd4993000
domain:    0
free list: 0xffffffff80f30e00

SEGMENT 7:

start:     0xd6fff000
end:       0xd7000000
domain:    0
free list: 0xffffffff80f30e00

SEGMENT 8:

start:     0x100001000
end:       0x211d4d000
domain:    0
free list: 0xffffffff80f30e00

SEGMENT 9:

start:     0x21fc00000
end:       0x21fd44000
domain:    0
free list: 0xffffffff80f30e00



>
> and from the crashdump:
> p pv_table

$1 = (struct pmap_large_md_page *) 0xfffffe000e000000

kgdb) p *pv_table
$1 = {pv_lock = {lock_object = {lo_name = 0xffffffff80b0a9ce "pmap pv 
list",
      lo_flags = 623050752, lo_data = 0, lo_witness = 0x800000000201f163}, 
    rw_lock = 1}, pv_page = {pv_list = {tqh_first = 0x0, 
      tqh_last = 0xfffffe000e000020}, pv_gen = 0, pat_mode = 0}, 
  pv_invl_gen = 0}
(kgdb) 


-- 
Cheers,
Cy Schubert <cy.schub...@cschubert.com>
FreeBSD UNIX:  <c...@freebsd.org>   Web:  http://www.FreeBSD.org

        The need of the many outweighs the greed of the few.


>
> On 10/7/19, Cy Schubert <cy.schub...@cschubert.com> wrote:
> > In message <201910070406.x9746n0u009...@slippy.cwsent.com>, Cy Schubert
> > writes:
> >> In message <201910062213.x96mdzv3085...@repo.freebsd.org>, Mateusz Guzik
> >> writes
> >> :
> >> > Author: mjg
> >> > Date: Sun Oct  6 22:13:35 2019
> >> > New Revision: 353149
> >> > URL: https://svnweb.freebsd.org/changeset/base/353149
> >> >
> >> > Log:
> >> >   amd64 pmap: implement per-superpage locks
> >> >
> >> >   The current 256-lock sized array is a problem in the following ways:
> >> >   - it's way too small
> >> >   - there are 2 locks per cacheline
> >> >   - it is not NUMA-aware
> >> >
> >> >   Solve these issues by introducing per-superpage locks backed by pages
> >> >   allocated from respective domains.
> >> >
> >> >   This significantly reduces contention e.g. during poudriere -j 104.
> >> >   See the review for results.
> >> >
> >> >   Reviewed by:   kib
> >> >   Discussed with:        jeff
> >> >   Sponsored by:  The FreeBSD Foundation
> >> >   Differential Revision: https://reviews.freebsd.org/D21833
> >> >
> >> > Modified:
> >> >   head/sys/amd64/amd64/pmap.c
> >> >
> >> > Modified: head/sys/amd64/amd64/pmap.c
> >> > ========================================================================
> ===
> >> ==
> >> > =
> >> > --- head/sys/amd64/amd64/pmap.c  Sun Oct  6 20:36:25 2019        (r35314
> >> > 8)
> >> > +++ head/sys/amd64/amd64/pmap.c  Sun Oct  6 22:13:35 2019        (r35314
> >> > 9)
> >> > @@ -316,13 +316,25 @@ pmap_pku_mask_bit(pmap_t pmap)
> >> >  #define PV_STAT(x)      do { } while (0)
> >> >  #endif
> >> >
> >> > -#define pa_index(pa)    ((pa) >> PDRSHIFT)
> >> > +#undef pa_index
> >> > +#define pa_index(pa)    ({                                      \
> >> > +        KASSERT((pa) <= vm_phys_segs[vm_phys_nsegs - 1].end,    \
> >> > +            ("address %lx beyond the last segment", (pa)));     \
> >> > +        (pa) >> PDRSHIFT;                                       \
> >> > +})
> >> > +#if VM_NRESERVLEVEL > 0
> >> > +#define pa_to_pmdp(pa)  (&pv_table[pa_index(pa)])
> >> > +#define pa_to_pvh(pa)   (&(pa_to_pmdp(pa)->pv_page))
> >> > +#define PHYS_TO_PV_LIST_LOCK(pa)        \
> >> > +                        (&(pa_to_pmdp(pa)->pv_lock))
> >> > +#else
> >> >  #define pa_to_pvh(pa)   (&pv_table[pa_index(pa)])
> >> >
> >> >  #define NPV_LIST_LOCKS  MAXCPU
> >> >
> >> >  #define PHYS_TO_PV_LIST_LOCK(pa)        \
> >> >                          (&pv_list_locks[pa_index(pa) % NPV_LIST_LOCKS])
> >> > +#endif
> >> >
> >> >  #define CHANGE_PV_LIST_LOCK_TO_PHYS(lockp, pa)  do {    \
> >> >          struct rwlock **_lockp = (lockp);               \
> >> > @@ -400,14 +412,22 @@ static int pmap_initialized;
> >> >
> >> >  /*
> >> >   * Data for the pv entry allocation mechanism.
> >> > - * Updates to pv_invl_gen are protected by the pv_list_locks[]
> >> > - * elements, but reads are not.
> >> > + * Updates to pv_invl_gen are protected by the pv list lock but reads
> >> > are
> >> no
> >> > t.
> >> >   */
> >> >  static TAILQ_HEAD(pch, pv_chunk) pv_chunks =
> >> > TAILQ_HEAD_INITIALIZER(pv_chu
> >> nk
> >> > s);
> >> >  static struct mtx __exclusive_cache_line pv_chunks_mutex;
> >> > +#if VM_NRESERVLEVEL > 0
> >> > +struct pmap_large_md_page {
> >> > +        struct rwlock   pv_lock;
> >> > +        struct md_page  pv_page;
> >> > +        u_long pv_invl_gen;
> >> > +};
> >> > +static struct pmap_large_md_page *pv_table;
> >> > +#else
> >> >  static struct rwlock __exclusive_cache_line
> >> > pv_list_locks[NPV_LIST_LOCKS];
> >> >  static u_long pv_invl_gen[NPV_LIST_LOCKS];
> >> >  static struct md_page *pv_table;
> >> > +#endif
> >> >  static struct md_page pv_dummy;
> >> >
> >> >  /*
> >> > @@ -918,12 +938,21 @@ SYSCTL_LONG(_vm_pmap, OID_AUTO, invl_wait_slow,
> >> > CTLFL
> >> A
> >> >      "Number of slow invalidation waits for lockless DI");
> >> >  #endif
> >> >
> >> > +#if VM_NRESERVLEVEL > 0
> >> >  static u_long *
> >> >  pmap_delayed_invl_genp(vm_page_t m)
> >> >  {
> >> >
> >> > +        return (&pa_to_pmdp(VM_PAGE_TO_PHYS(m))->pv_invl_gen);
> >> > +}
> >> > +#else
> >> > +static u_long *
> >> > +pmap_delayed_invl_genp(vm_page_t m)
> >> > +{
> >> > +
> >> >          return (&pv_invl_gen[pa_index(VM_PAGE_TO_PHYS(m)) % NPV_LIST_LO
> CKS]);
> >> >  }
> >> > +#endif
> >> >
> >> >  static void
> >> >  pmap_delayed_invl_callout_func(void *arg __unused)
> >> > @@ -1803,6 +1832,112 @@ pmap_page_init(vm_page_t m)
> >> >          m->md.pat_mode = PAT_WRITE_BACK;
> >> >  }
> >> >
> >> > +#if VM_NRESERVLEVEL > 0
> >> > +static void
> >> > +pmap_init_pv_table(void)
> >> > +{
> >> > +        struct pmap_large_md_page *pvd;
> >> > +        vm_size_t s;
> >> > +        long start, end, highest, pv_npg;
> >> > +        int domain, i, j, pages;
> >> > +
> >> > +        /*
> >> > +         * We strongly depend on the size being a power of two, so the 
> assert
> >> > +         * is overzealous. However, should the struct be resized to a
> >> > +         * different power of two, the code below needs to be revisited
> .
> >> > +         */
> >> > +        CTASSERT((sizeof(*pvd) == 64));
> >> > +
> >> > +        /*
> >> > +         * Calculate the size of the array.
> >> > +         */
> >> > +        pv_npg = howmany(vm_phys_segs[vm_phys_nsegs - 1].end, NBPDR);
> >> > +        s = (vm_size_t)pv_npg * sizeof(struct pmap_large_md_page);
> >> > +        s = round_page(s);
> >> > +        pv_table = (struct pmap_large_md_page *)kva_alloc(s);
> >> > +        if (pv_table == NULL)
> >> > +                panic("%s: kva_alloc failed\n", __func__);
> >> > +
> >> > +        /*
> >> > +         * Iterate physical segments to allocate space for respective p
> ages.
> >> > +         */
> >> > +        highest = -1;
> >> > +        s = 0;
> >> > +        for (i = 0; i < vm_phys_nsegs; i++) {
> >> > +                start = vm_phys_segs[i].start / NBPDR;
> >> > +                end = vm_phys_segs[i].end / NBPDR;
> >> > +                domain = vm_phys_segs[i].domain;
> >> > +
> >> > +                if (highest >= end)
> >> > +                        continue;
> >> > +
> >> > +                if (start < highest) {
> >> > +                        start = highest + 1;
> >> > +                        pvd = &pv_table[start];
> >> > +                } else {
> >> > +                        /*
> >> > +                         * The lowest address may land somewhere in the
>  middle
> >> > +                         * of our page. Simplify the code by pretending
>  it is
> >> > +                         * at the beginning.
> >> > +                         */
> >> > +                        pvd = pa_to_pmdp(vm_phys_segs[i].start);
> >> > +                        pvd = (struct pmap_large_md_page *)trunc_page(p
> vd);
> >> > +                        start = pvd - pv_table;
> >> > +                }
> >> > +
> >> > +                pages = end - start + 1;
> >> > +                s = round_page(pages * sizeof(*pvd));
> >> > +                highest = start + (s / sizeof(*pvd)) - 1;
> >> > +
> >> > +                for (j = 0; j < s; j += PAGE_SIZE) {
> >> > +                        vm_page_t m = vm_page_alloc_domain(NULL, 0,
> >> > +                            domain, VM_ALLOC_NORMAL | VM_ALLOC_NOOBJ);
> >> > +                        if (m == NULL)
> >> > +                                panic("vm_page_alloc_domain failed for 
> %lx\n",
> >> > (vm_offset_t)pvd + j);
> >> > +                        pmap_qenter((vm_offset_t)pvd + j, &m, 1);
> >> > +                }
> >> > +
> >> > +                for (j = 0; j < s / sizeof(*pvd); j++) {
> >> > +                        rw_init_flags(&pvd->pv_lock, "pmap pv list", RW
> _NEW);
> >> > +                        TAILQ_INIT(&pvd->pv_page.pv_list);
> >> > +                        pvd->pv_page.pv_gen = 0;
> >> > +                        pvd->pv_page.pat_mode = 0;
> >> > +                        pvd->pv_invl_gen = 0;
> >> > +                        pvd++;
> >> > +                }
> >> > +        }
> >> > +        TAILQ_INIT(&pv_dummy.pv_list);
> >> > +}
> >> > +#else
> >> > +static void
> >> > +pmap_init_pv_table(void)
> >> > +{
> >> > +        vm_size_t s;
> >> > +        long i, pv_npg;
> >> > +
> >> > +        /*
> >> > +         * Initialize the pool of pv list locks.
> >> > +         */
> >> > +        for (i = 0; i < NPV_LIST_LOCKS; i++)
> >> > +                rw_init(&pv_list_locks[i], "pmap pv list");
> >> > +
> >> > +        /*
> >> > +         * Calculate the size of the pv head table for superpages.
> >> > +         */
> >> > +        pv_npg = howmany(vm_phys_segs[vm_phys_nsegs - 1].end, NBPDR);
> >> > +
> >> > +        /*
> >> > +         * Allocate memory for the pv head table for superpages.
> >> > +         */
> >> > +        s = (vm_size_t)pv_npg * sizeof(struct md_page);
> >> > +        s = round_page(s);
> >> > +        pv_table = (struct md_page *)kmem_malloc(s, M_WAITOK | M_ZERO);
> >> > +        for (i = 0; i < pv_npg; i++)
> >> > +                TAILQ_INIT(&pv_table[i].pv_list);
> >> > +        TAILQ_INIT(&pv_dummy.pv_list);
> >> > +}
> >> > +#endif
> >> > +
> >> >  /*
> >> >   *      Initialize the pmap module.
> >> >   *      Called by vm_init, to initialize any structures that the pmap
> >> > @@ -1813,8 +1948,7 @@ pmap_init(void)
> >> >  {
> >> >          struct pmap_preinit_mapping *ppim;
> >> >          vm_page_t m, mpte;
> >> > -        vm_size_t s;
> >> > -        int error, i, pv_npg, ret, skz63;
> >> > +        int error, i, ret, skz63;
> >> >
> >> >          /* L1TF, reserve page @0 unconditionally */
> >> >          vm_page_blacklist_add(0, bootverbose);
> >> > @@ -1902,26 +2036,7 @@ pmap_init(void)
> >> >           */
> >> >          mtx_init(&pv_chunks_mutex, "pmap pv chunk list", NULL, MTX_DEF)
> ;
> >> >
> >> > -        /*
> >> > -         * Initialize the pool of pv list locks.
> >> > -         */
> >> > -        for (i = 0; i < NPV_LIST_LOCKS; i++)
> >> > -                rw_init(&pv_list_locks[i], "pmap pv list");
> >> > -
> >> > -        /*
> >> > -         * Calculate the size of the pv head table for superpages.
> >> > -         */
> >> > -        pv_npg = howmany(vm_phys_segs[vm_phys_nsegs - 1].end, NBPDR);
> >> > -
> >> > -        /*
> >> > -         * Allocate memory for the pv head table for superpages.
> >> > -         */
> >> > -        s = (vm_size_t)(pv_npg * sizeof(struct md_page));
> >> > -        s = round_page(s);
> >> > -        pv_table = (struct md_page *)kmem_malloc(s, M_WAITOK | M_ZERO);
> >> > -        for (i = 0; i < pv_npg; i++)
> >> > -                TAILQ_INIT(&pv_table[i].pv_list);
> >> > -        TAILQ_INIT(&pv_dummy.pv_list);
> >> > +        pmap_init_pv_table();
> >> >
> >> >          pmap_initialized = 1;
> >> >          for (i = 0; i < PMAP_PREINIT_MAPPING_COUNT; i++) {
> >> >
> >>
> >> This causes a page fault during X (xdm) startup, which loads
> >> drm-current-kmod.
> >>
> >> db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame
> >> 0xfffffe0093e9c260
> >> vpanic() at vpanic+0x19d/frame 0xfffffe0093e9c2b0
> >> panic() at panic+0x43/frame 0xfffffe0093e9c310
> >> vm_fault() at vm_fault+0x2126/frame 0xfffffe0093e9c460
> >> vm_fault_trap() at vm_fault_trap+0x73/frame 0xfffffe0093e9c4b0
> >> trap_pfault() at trap_pfault+0x1b6/frame 0xfffffe0093e9c510
> >> trap() at trap+0x2a1/frame 0xfffffe0093e9c620
> >> calltrap() at calltrap+0x8/frame 0xfffffe0093e9c620
> >> --- trap 0xc, rip = 0xffffffff80a054b1, rsp = 0xfffffe0093e9c6f0, rbp =
> >> 0xfffffe0093e9c7a0 ---
> >> pmap_enter() at pmap_enter+0x861/frame 0xfffffe0093e9c7a0
> >> vm_fault() at vm_fault+0x1c69/frame 0xfffffe0093e9c8f0
> >> vm_fault_trap() at vm_fault_trap+0x73/frame 0xfffffe0093e9c940
> >> trap_pfault() at trap_pfault+0x1b6/frame 0xfffffe0093e9c9a0
> >> trap() at trap+0x438/frame 0xfffffe0093e9cab0
> >> calltrap() at calltrap+0x8/frame 0xfffffe0093e9cab0
> >> --- trap 0xc, rip = 0x30e2a9c3, rsp = 0x7fffffffea50, rbp = 0x7fffffffeaa0
> >>
> >> ---
> >> Uptime: 3m33s
> >> Dumping 945 out of 7974
> >> MB:..2%..11%..21%..31%..41%..51%..61%..72%..82%..92%
> >>
> >> (kgdb) bt
> >> #0  doadump (textdump=1) at pcpu_aux.h:55
> >> #1  0xffffffff8068c5ed in kern_reboot (howto=260)
> >>     at /opt/src/svn-current/sys/kern/kern_shutdown.c:479
> >> #2  0xffffffff8068caa9 in vpanic (fmt=<value optimized out>,
> >>     ap=<value optimized out>)
> >>     at /opt/src/svn-current/sys/kern/kern_shutdown.c:908
> >> #3  0xffffffff8068c8a3 in panic (fmt=<value optimized out>)
> >>     at /opt/src/svn-current/sys/kern/kern_shutdown.c:835
> >> #4  0xffffffff8098c966 in vm_fault (map=<value optimized out>,
> >>     vaddr=<value optimized out>, fault_type=<value optimized out>,
> >>     fault_flags=<value optimized out>, m_hold=<value optimized out>)
> >>     at /opt/src/svn-current/sys/vm/vm_fault.c:672
> >> #5  0xffffffff8098a723 in vm_fault_trap (map=0xfffff80002001000,
> >>     vaddr=<value optimized out>, fault_type=2 '\002',
> >>     fault_flags=<value optimized out>, signo=0x0, ucode=0x0)
> >>     at /opt/src/svn-current/sys/vm/vm_fault.c:568
> >> #6  0xffffffff80a18326 in trap_pfault (frame=0xfffffe0093e9c630,
> >>     signo=<value optimized out>, ucode=<value optimized out>)
> >>     at /opt/src/svn-current/sys/amd64/amd64/trap.c:828
> >> #7  0xffffffff80a177f1 in trap (frame=0xfffffe0093e9c630)
> >>     at /opt/src/svn-current/sys/amd64/amd64/trap.c:407
> >> #8  0xffffffff809f1aac in calltrap ()
> >>     at /opt/src/svn-current/sys/amd64/amd64/exception.S:289
> >> ---Type <return> to continue, or q <return> to quit---
> >> #9  0xffffffff80a054b1 in pmap_enter (pmap=<value optimized out>,
> >>     va=851443712, m=0xfffffe0005b25ce8, prot=<value optimized out>,
> >>     flags=2677542912, psind=<value optimized out>) at atomic.h:221
> >> #10 0xffffffff8098c4a9 in vm_fault (map=<value optimized out>,
> >>     vaddr=<value optimized out>, fault_type=232 '\ufffd',
> >>     fault_flags=<value optimized out>, m_hold=0x0)
> >>     at /opt/src/svn-current/sys/vm/vm_fault.c:489
> >> #11 0xffffffff8098a723 in vm_fault_trap (map=0xfffff80173eb5000,
> >>     vaddr=<value optimized out>, fault_type=2 '\002',
> >>     fault_flags=<value optimized out>, signo=0xfffffe0093e9ca84,
> >>     ucode=0xfffffe0093e9ca80) at
> >> /opt/src/svn-current/sys/vm/vm_fault.c:568
> >> #12 0xffffffff80a18326 in trap_pfault (frame=0xfffffe0093e9cac0,
> >>     signo=<value optimized out>, ucode=<value optimized out>)
> >>     at /opt/src/svn-current/sys/amd64/amd64/trap.c:828
> >> #13 0xffffffff80a17988 in trap (frame=0xfffffe0093e9cac0)
> >>     at /opt/src/svn-current/sys/amd64/amd64/trap.c:347
> >> #14 0xffffffff809f1aac in calltrap ()
> >>     at /opt/src/svn-current/sys/amd64/amd64/exception.S:289
> >> #15 0x0000000030e2a9c3 in ?? ()
> >> Previous frame inner to this frame (corrupt stack?)
> >> Current language:  auto; currently minimal
> >> (kgdb) frame 9
> >> #9  0xffffffff80a054b1 in pmap_enter (pmap=<value optimized out>,
> >>     va=851443712, m=0xfffffe0005b25ce8, prot=<value optimized out>,
> >>     flags=2677542912, psind=<value optimized out>) at atomic.h:221
> >> 221        ATOMIC_CMPSET(long);
> >> (kgdb) l
> >> 216        }
> >> 217        
> >> 218        ATOMIC_CMPSET(char);
> >> 219        ATOMIC_CMPSET(short);
> >> 220        ATOMIC_CMPSET(int);
> >> 221        ATOMIC_CMPSET(long);
> >> 222        
> >> 223        /*
> >> 224         * Atomically add the value of v to the integer pointed to by p
>  and
> >> return
> >> 225         * the previous value of *p.
> >> (kgdb)
> >
> > I should use kgdb from ports instead of /usr/libexec version. Similar
> > result.
> >
> > <4>WARN_ON(!mutex_is_locked(&fbc->lock))WARN_ON(!mutex_is_locked(&fbc->
> > lock))
> > panic: vm_fault: fault on nofault entry, addr: 0xfffffe000e01c000
> > cpuid = 1
> > time = 1570417211
> > KDB: stack backtrace:
> > db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame
> > 0xfffffe0093e9c260
> > vpanic() at vpanic+0x19d/frame 0xfffffe0093e9c2b0
> > panic() at panic+0x43/frame 0xfffffe0093e9c310
> > vm_fault() at vm_fault+0x2126/frame 0xfffffe0093e9c460
> > vm_fault_trap() at vm_fault_trap+0x73/frame 0xfffffe0093e9c4b0
> > trap_pfault() at trap_pfault+0x1b6/frame 0xfffffe0093e9c510
> > trap() at trap+0x2a1/frame 0xfffffe0093e9c620
> > calltrap() at calltrap+0x8/frame 0xfffffe0093e9c620
> > --- trap 0xc, rip = 0xffffffff80a054b1, rsp = 0xfffffe0093e9c6f0, rbp =
> > 0xfffffe0093e9c7a0 ---
> > pmap_enter() at pmap_enter+0x861/frame 0xfffffe0093e9c7a0
> > vm_fault() at vm_fault+0x1c69/frame 0xfffffe0093e9c8f0
> > vm_fault_trap() at vm_fault_trap+0x73/frame 0xfffffe0093e9c940
> > trap_pfault() at trap_pfault+0x1b6/frame 0xfffffe0093e9c9a0
> > trap() at trap+0x438/frame 0xfffffe0093e9cab0
> > calltrap() at calltrap+0x8/frame 0xfffffe0093e9cab0
> > --- trap 0xc, rip = 0x30e2a9c3, rsp = 0x7fffffffea50, rbp = 0x7fffffffeaa0
> > ---
> > Uptime: 3m33s
> > Dumping 945 out of 7974
> > MB:..2%..11%..21%..31%..41%..51%..61%..72%..82%..92%
> >
> > __curthread () at /opt/src/svn-current/sys/amd64/include/pcpu_aux.h:55
> > 55          __asm("movq %%gs:%P1,%0" : "=r" (td) : "n" (offsetof(struct pcp
> u,
> > (kgdb)
> >
> > Backtrace stopped: Cannot access memory at address 0x7fffffffea50
> > (kgdb) frame 10
> > #10 0xffffffff80a054b1 in atomic_fcmpset_long (dst=<optimized out>,
> >     src=<optimized out>, expect=<optimized out>)
> >     at /opt/src/svn-current/sys/amd64/include/atomic.h:221
> > 221 ATOMIC_CMPSET(long);
> > (kgdb) l
> > 216 }
> > 217 
> > 218 ATOMIC_CMPSET(char);
> > 219 ATOMIC_CMPSET(short);
> > 220 ATOMIC_CMPSET(int);
> > 221 ATOMIC_CMPSET(long);
> > 222 
> > 223 /*
> > 224  * Atomically add the value of v to the integer pointed to by p and
> > return
> > 225  * the previous value of *p.
> > (kgdb)
> >
> >
> >
> > --
> > Cheers,
> > Cy Schubert <cy.schub...@cschubert.com>
> > FreeBSD UNIX:  <c...@freebsd.org>   Web:  http://www.FreeBSD.org
> >
> >     The need of the many outweighs the greed of the few.
> >
> >
> >
>
>
> -- 
> Mateusz Guzik <mjguzik gmail.com>




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