On Thu, Feb 12, 2009 at 11:21:13AM +0100, Ingo Molnar wrote: > > * Ingo Molnar <mingo@xxxxxxx> wrote: > > > Frederic, could you try the patch below? > > Please try v2 below - it might even build ;-) > > Ingo Ok, I tested it through 3 bootups and it did not triggered. But it's absolutely not a guarantee, as I said, I tried to reproduce it with several bootups yesterday and I couln't see it again. But by reading the warning and your patch, yes it is supposed to solve it :) BTW, a small thing: > [ 45.228589] hardirqs last disabled at (0): [<ffffffff8025449d>] copy_process+0x68d/0x1500 > [ 45.228602] softirqs last enabled at (0): [<ffffffff8025449d>] copy_process+0x68d/0x1500 The reason for which I wanted to send an irqsoff trace is that the above lines are false. addr2line -e vmlinux ffffffff8025449d /home/me/linux/rt/linux-2.6.29-rc4/kernel/fork.c:1107 (before your patch) Which is this area in copy_process: #ifdef CONFIG_NUMA p->mempolicy = mpol_dup(p->mempolicy); if (IS_ERR(p->mempolicy)) { retval = PTR_ERR(p->mempolicy); p->mempolicy = NULL; goto bad_fork_cleanup_cgroup; } mpol_fix_fork_child_flag(p); // <-- 1107 #endif Nothing here disables irq. That's why I wanted to provide an irqsoff trace. But, heh I only had to read res_counter_charge() :-) Anyway, there is a problem with these hardirqs/softirqs last disabled... > [ 45.228609] softirqs last disabled at (0): [<(null)>] (null) > [ 45.228617] Pid: 4290, comm: ntpdate Tainted: G W 2.6.29-rc4-rt1-tip #1 > [ 45.228622] Call Trace: > [ 45.228632] [<ffffffff8027dfb0>] ? print_irqtrace_events+0xd0/0xe0 > [ 45.228639] [<ffffffff8024cd73>] __might_sleep+0x113/0x130 > [ 45.228646] [<ffffffff8077c811>] rt_spin_lock+0xa1/0xb0 > [ 45.228653] [<ffffffff80296a3d>] res_counter_charge+0x5d/0x130 > [ 45.228660] [<ffffffff802fb67f>] __mem_cgroup_try_charge+0x7f/0x180 > [ 45.228667] [<ffffffff802fc407>] mem_cgroup_charge_common+0x57/0x90 > [ 45.228674] [<ffffffff80212096>] ? ftrace_call+0x5/0x2b > [ 45.228680] [<ffffffff802fc49d>] mem_cgroup_newpage_charge+0x5d/0x60 > [ 45.228688] [<ffffffff802d94ce>] __do_fault+0x29e/0x4c0 > [ 45.228694] [<ffffffff8077c843>] ? rt_spin_unlock+0x23/0x80 > [ 45.228700] [<ffffffff802db8b5>] handle_mm_fault+0x205/0x890 > [ 45.228707] [<ffffffff80212096>] ? ftrace_call+0x5/0x2b > [ 45.228714] [<ffffffff8023495e>] do_page_fault+0x11e/0x2a0 > [ 45.228720] [<ffffffff8077e5a5>] page_fault+0x25/0x30 > [ 45.228727] [<ffffffff8043e1ed>] ? __clear_user+0x3d/0x70 > [ 45.228733] [<ffffffff8043e1d1>] ? __clear_user+0x21/0x70 > > The reason is the raw IRQ flag use of kernel/res_counter.c. > > The irq flags tricks there seem a bit pointless: it cannot > protect the c->parent linkage because local_irq_save() is > only per CPU. > > So replace it with _nort(). This code needs a second look. > > Reported-by: Frederic Weisbecker <fweisbec@xxxxxxxxx> > Signed-off-by: Ingo Molnar <mingo@xxxxxxx> > --- > kernel/res_counter.c | 9 +++++---- > 1 file changed, 5 insertions(+), 4 deletions(-) > > Index: tip/kernel/res_counter.c > =================================================================== > --- tip.orig/kernel/res_counter.c > +++ tip/kernel/res_counter.c > @@ -14,6 +14,7 @@ > #include <linux/res_counter.h> > #include <linux/uaccess.h> > #include <linux/mm.h> > +#include <linux/interrupt.h> > > void res_counter_init(struct res_counter *counter, struct res_counter *parent) > { > @@ -43,7 +44,7 @@ int res_counter_charge(struct res_counte > struct res_counter *c, *u; > > *limit_fail_at = NULL; > - local_irq_save(flags); > + local_irq_save_nort(flags); > for (c = counter; c != NULL; c = c->parent) { > spin_lock(&c->lock); > ret = res_counter_charge_locked(c, val); > @@ -62,7 +63,7 @@ undo: > spin_unlock(&u->lock); > } > done: > - local_irq_restore(flags); > + local_irq_restore_nort(flags); > return ret; > } > > @@ -79,13 +80,13 @@ void res_counter_uncharge(struct res_cou > unsigned long flags; > struct res_counter *c; > > - local_irq_save(flags); > + local_irq_save_nort(flags); > for (c = counter; c != NULL; c = c->parent) { > spin_lock(&c->lock); > res_counter_uncharge_locked(c, val); > spin_unlock(&c->lock); > } > - local_irq_restore(flags); > + local_irq_restore_nort(flags); > } > > -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html