Date: Thu, 22 Jan 2015 10:35:14 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Ryan Stone <rysto32@gmail.com> Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: Re: Sleeping thread held mutex in vm_pageout_oom() Message-ID: <20150122083514.GU42409@kib.kiev.ua> In-Reply-To: <CAFMmRNz6Dof%2B95zyekUFEbmcqeFSqXr96Y7BUZpqJ9z0XoWVOA@mail.gmail.com> References: <CAFMmRNxz252HMWWBmRf=Z69zh2_w9cD5e1AZGeizyagKezm2Hw@mail.gmail.com> <20150120083212.GC42409@kib.kiev.ua> <CAFMmRNz6Dof%2B95zyekUFEbmcqeFSqXr96Y7BUZpqJ9z0XoWVOA@mail.gmail.com>
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On Wed, Jan 21, 2015 at 09:04:51PM -0500, Ryan Stone wrote: > Thanks for the patch. I tried it out this afternoon and got the > following panic: > > panic: PHOLD of exiting process^M^M > cpuid = 9^M^M > curthread = pagedaemon/pagedaemon (8/100154)^M^M > cpu_ticks = 979566002403^M^M > KDB: stack backtrace:^M^M > db_trace_self_wrapper() at 0xffffffff801e672a = db_trace_self_wrapper+0x2a^M^M > panic() at 0xffffffff80480818 = panic+0x228^M^M > vm_pageout_oom() at 0xffffffff80669a9b = vm_pageout_oom+0x58b^M^M > vm_pageout() at 0xffffffff8066aa35 = vm_pageout+0x975^M^M > fork_exit() at 0xffffffff80454ada = fork_exit+0x12a^M^M > fork_trampoline() at 0xffffffff8067b37e = fork_trampoline+0xe^M^M > > > I believe that we need to check for P_WEXIT before considering p as a > candidate to be killed: Sure, you are right. I also took opportunity to reformat the condition and to remove excessive () there. diff --git a/sys/vm/vm_pageout.c b/sys/vm/vm_pageout.c index ca9d7f9..d2e0483 100644 --- a/sys/vm/vm_pageout.c +++ b/sys/vm/vm_pageout.c @@ -1516,15 +1542,15 @@ vm_pageout_oom(int shortage) FOREACH_PROC_IN_SYSTEM(p) { int breakout; - if (PROC_TRYLOCK(p) == 0) - continue; + PROC_LOCK(p); + /* * If this is a system, protected or killed process, skip it. */ - if (p->p_state != PRS_NORMAL || - (p->p_flag & (P_INEXEC | P_PROTECTED | P_SYSTEM)) || - (p->p_pid == 1) || P_KILLED(p) || - ((p->p_pid < 48) && (swap_pager_avail != 0))) { + if (p->p_state != PRS_NORMAL || (p->p_flag & (P_INEXEC | + P_PROTECTED | P_SYSTEM | P_WEXIT)) != 0 || + p->p_pid == 1 || P_KILLED(p) || + (p->p_pid < 48 && swap_pager_avail != 0)) { PROC_UNLOCK(p); continue; } @@ -1557,11 +1583,14 @@ vm_pageout_oom(int shortage) PROC_UNLOCK(p); continue; } + _PHOLD(p); if (!vm_map_trylock_read(&vm->vm_map)) { - vmspace_free(vm); + _PRELE(p); PROC_UNLOCK(p); + vmspace_free(vm); continue; } + PROC_UNLOCK(p); size = vmspace_swap_count(vm); vm_map_unlock_read(&vm->vm_map); if (shortage == VM_OOM_MEM) @@ -1573,16 +1602,19 @@ vm_pageout_oom(int shortage) */ if (size > bigsize) { if (bigproc != NULL) - PROC_UNLOCK(bigproc); + PRELE(bigproc); bigproc = p; bigsize = size; - } else - PROC_UNLOCK(p); + } else { + PRELE(p); + } } sx_sunlock(&allproc_lock); if (bigproc != NULL) { + PROC_LOCK(bigproc); killproc(bigproc, "out of swap space"); sched_nice(bigproc, PRIO_MIN); + _PRELE(bigproc); PROC_UNLOCK(bigproc); wakeup(&vm_cnt.v_free_count); }
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