Messages in this thread Patch in this message | | | Date | Wed, 31 Oct 2018 10:33:49 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH RFC kenrel/rcu] Eliminate BUG_ON() for sync.c |
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On Wed, Oct 31, 2018 at 06:26:05PM +0100, Oleg Nesterov wrote: > On 10/30, Paul E. McKenney wrote: > > > > On Mon, Oct 22, 2018 at 06:14:40PM +0200, Oleg Nesterov wrote: > > > > > ---------------------------------------------------------------------------- > > > > > Damn. > > > > > > > > > > This suddenly reminds me that I rewrote this code completely, and you even > > > > > reviewed the new implementation and (iirc) acked it! > > > > > > > > > > However, I failed to force myself to rewrite the comments, and that is why > > > > > I didn't send the "official" patch :/ > > > > > > > > > > May be some time... > > > > > > > > Could you please point me at the last email thread? Yes, I should be > > > > able to find it, but I would probably get the wrong one. :-/ > > > > > > probably this one, > > > > > > [PATCH] rcu_sync: simplify the state machine, introduce __rcu_sync_enter() > > > https://lkml.org/lkml/2016/7/16/150 > > > > > > but I am not sure, will recheck tomorrow. > > > > Just following up... Here is what I currently have. > > Hmm. Are you sure you replied to the correct message? ;) > > the patch below looks absolutely unrelated...
Oy... Right message, wrong commit.
Does the one below look somewhat more relevant? ;-)
Thanx, Paul
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commit 10314fde6fcdbaaf7c21b539dd2db5933344344f Author: Paul E. McKenney <paulmck@linux.ibm.com> Date: Mon Oct 22 07:43:22 2018 -0700
rcu: Eliminate BUG_ON() for sync.c The sync.c file has a number of calls to BUG_ON(), which panics the kernel, which is not a good strategy for devices (like embedded) that don't have a way to capture console output. This commit therefore changes these BUG_ON() calls to WARN_ON_ONCE(), but does so quite naively. Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org>
diff --git a/kernel/rcu/sync.c b/kernel/rcu/sync.c index 3f943efcf61c..a6ba446a9693 100644 --- a/kernel/rcu/sync.c +++ b/kernel/rcu/sync.c @@ -125,8 +125,7 @@ void rcu_sync_enter(struct rcu_sync *rsp) rsp->gp_state = GP_PENDING; spin_unlock_irq(&rsp->rss_lock); - BUG_ON(need_wait && need_sync); - + WARN_ON_ONCE(need_wait && need_sync); if (need_sync) { gp_ops[rsp->gp_type].sync(); rsp->gp_state = GP_PASSED; @@ -139,7 +138,7 @@ void rcu_sync_enter(struct rcu_sync *rsp) * Nobody has yet been allowed the 'fast' path and thus we can * avoid doing any sync(). The callback will get 'dropped'. */ - BUG_ON(rsp->gp_state != GP_PASSED); + WARN_ON_ONCE(rsp->gp_state != GP_PASSED); } } @@ -166,8 +165,8 @@ static void rcu_sync_func(struct rcu_head *rhp) struct rcu_sync *rsp = container_of(rhp, struct rcu_sync, cb_head); unsigned long flags; - BUG_ON(rsp->gp_state != GP_PASSED); - BUG_ON(rsp->cb_state == CB_IDLE); + WARN_ON_ONCE(rsp->gp_state != GP_PASSED); + WARN_ON_ONCE(rsp->cb_state == CB_IDLE); spin_lock_irqsave(&rsp->rss_lock, flags); if (rsp->gp_count) { @@ -225,7 +224,7 @@ void rcu_sync_dtor(struct rcu_sync *rsp) { int cb_state; - BUG_ON(rsp->gp_count); + WARN_ON_ONCE(rsp->gp_count); spin_lock_irq(&rsp->rss_lock); if (rsp->cb_state == CB_REPLAY) @@ -235,6 +234,6 @@ void rcu_sync_dtor(struct rcu_sync *rsp) if (cb_state != CB_IDLE) { gp_ops[rsp->gp_type].wait(); - BUG_ON(rsp->cb_state != CB_IDLE); + WARN_ON_ONCE(rsp->cb_state != CB_IDLE); } }
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