search for: seqlock

...e many factors that may slow down the > > > synchronize_rcu() which makes it unsuitable to be called in MMU > > > notifier. > > > > > > A solution is SRCU but its overhead is obvious with the expensive full > > > memory barrier. Another choice is to use seqlock, but it doesn't > > > provide a synchronization method between readers and writers. The last > > > choice is to use vq mutex, but it need to deal with the worst case > > > that MMU notifier must be blocked and wait for the finish of swap in. > > > > >...

...e many factors that may slow down the > > > synchronize_rcu() which makes it unsuitable to be called in MMU > > > notifier. > > > > > > A solution is SRCU but its overhead is obvious with the expensive full > > > memory barrier. Another choice is to use seqlock, but it doesn't > > > provide a synchronization method between readers and writers. The last > > > choice is to use vq mutex, but it need to deal with the worst case > > > that MMU notifier must be blocked and wait for the finish of swap in. > > > > >...

...t; > > synchronize_rcu() which makes it unsuitable to be called in MMU > > > > > notifier. > > > > > > > > > > A solution is SRCU but its overhead is obvious with the expensive full > > > > > memory barrier. Another choice is to use seqlock, but it doesn't > > > > > provide a synchronization method between readers and writers. The last > > > > > choice is to use vq mutex, but it need to deal with the worst case > > > > > that MMU notifier must be blocked and wait for the finish of swap...

...t; > > synchronize_rcu() which makes it unsuitable to be called in MMU > > > > > notifier. > > > > > > > > > > A solution is SRCU but its overhead is obvious with the expensive full > > > > > memory barrier. Another choice is to use seqlock, but it doesn't > > > > > provide a synchronization method between readers and writers. The last > > > > > choice is to use vq mutex, but it need to deal with the worst case > > > > > that MMU notifier must be blocked and wait for the finish of swap...

...;>>> synchronize_rcu() which makes it unsuitable to be called in MMU >>>>>> notifier. >>>>>> >>>>>> A solution is SRCU but its overhead is obvious with the expensive full >>>>>> memory barrier. Another choice is to use seqlock, but it doesn't >>>>>> provide a synchronization method between readers and writers. The last >>>>>> choice is to use vq mutex, but it need to deal with the worst case >>>>>> that MMU notifier must be blocked and wait for the finish of swap...

..._start(). But on a busy > system, there would be many factors that may slow down the > synchronize_rcu() which makes it unsuitable to be called in MMU > notifier. > > A solution is SRCU but its overhead is obvious with the expensive full > memory barrier. Another choice is to use seqlock, but it doesn't > provide a synchronization method between readers and writers. The last > choice is to use vq mutex, but it need to deal with the worst case > that MMU notifier must be blocked and wait for the finish of swap in. > > So this patch switches use a counter to track...

..._start(). But on a busy > system, there would be many factors that may slow down the > synchronize_rcu() which makes it unsuitable to be called in MMU > notifier. > > A solution is SRCU but its overhead is obvious with the expensive full > memory barrier. Another choice is to use seqlock, but it doesn't > provide a synchronization method between readers and writers. The last > choice is to use vq mutex, but it need to deal with the worst case > that MMU notifier must be blocked and wait for the finish of swap in. > > So this patch switches use a counter to track...

...ctors that may slow down the >>>> synchronize_rcu() which makes it unsuitable to be called in MMU >>>> notifier. >>>> >>>> A solution is SRCU but its overhead is obvious with the expensive full >>>> memory barrier. Another choice is to use seqlock, but it doesn't >>>> provide a synchronization method between readers and writers. The last >>>> choice is to use vq mutex, but it need to deal with the worst case >>>> that MMU notifier must be blocked and wait for the finish of swap in. >>>> &gt...

Stephen Hemminger <sthemmin at microsoft.com> writes: > Why not use existing seqlock's? > To be honest I don't quite understand how we could use it -- the sequence locking here is done against the page updated by the hypersior, we're not creating new structures (so I don't understand how we could use struct seqcount which we don't have) but I may be misunder...

Stephen Hemminger <sthemmin at microsoft.com> writes: > Why not use existing seqlock's? > To be honest I don't quite understand how we could use it -- the sequence locking here is done against the page updated by the hypersior, we're not creating new structures (so I don't understand how we could use struct seqcount which we don't have) but I may be misunder...

...ze MMU notifier with worker. This leads > calling synchronize_rcu() in invalidate_range_start(). But on a busy > system, there would be many factors that may slow down the > synchronize_rcu() which makes it unsuitable to be called in MMU > notifier. > > So this patch switches use seqlock counter to track whether or not the > map was used. The counter was increased when vq try to start or finish > uses the map. This means, when it was even, we're sure there's no > readers and MMU notifier is synchronized. When it was odd, it means > there's a reader we need t...

...ze MMU notifier with worker. This leads > calling synchronize_rcu() in invalidate_range_start(). But on a busy > system, there would be many factors that may slow down the > synchronize_rcu() which makes it unsuitable to be called in MMU > notifier. > > So this patch switches use seqlock counter to track whether or not the > map was used. The counter was increased when vq try to start or finish > uses the map. This means, when it was even, we're sure there's no > readers and MMU notifier is synchronized. When it was odd, it means > there's a reader we need t...

...r ?...? before ?spinlock_t? In file included from include/linux/time.h:7, from include/linux/timex.h:57, from include/linux/sched.h:48, from include/linux/module.h:9, from /usr/src/dahdi/drivers/dahdi/dahdi-base.c:40: include/linux/seqlock.h:34: error: expected specifier-qualifier-list before ?spinlock_t? include/linux/seqlock.h: In function ?write_seqlock?: include/linux/seqlock.h:62: error: implicit declaration of function ?_spin_lock? include/linux/seqlock.h:62: error: ?seqlock_t? has no member named ?lock? include/linux/seqlock.h...

...;> calling synchronize_rcu() in invalidate_range_start(). But on a busy >>> system, there would be many factors that may slow down the >>> synchronize_rcu() which makes it unsuitable to be called in MMU >>> notifier. >>> >>> So this patch switches use seqlock counter to track whether or not the >>> map was used. The counter was increased when vq try to start or finish >>> uses the map. This means, when it was even, we're sure there's no >>> readers and MMU notifier is synchronized. When it was odd, it means >>&gt...

...rker. This leads >> calling synchronize_rcu() in invalidate_range_start(). But on a busy >> system, there would be many factors that may slow down the >> synchronize_rcu() which makes it unsuitable to be called in MMU >> notifier. >> >> So this patch switches use seqlock counter to track whether or not the >> map was used. The counter was increased when vq try to start or finish >> uses the map. This means, when it was even, we're sure there's no >> readers and MMU notifier is synchronized. When it was odd, it means >> there's a...

...>> system, there would be many factors that may slow down the >> synchronize_rcu() which makes it unsuitable to be called in MMU >> notifier. >> >> A solution is SRCU but its overhead is obvious with the expensive full >> memory barrier. Another choice is to use seqlock, but it doesn't >> provide a synchronization method between readers and writers. The last >> choice is to use vq mutex, but it need to deal with the worst case >> that MMU notifier must be blocked and wait for the finish of swap in. >> >> So this patch switches use...

From: Eric Dumazet <edumazet at google.com> commit 3fa2a1df909 (virtio-net: per cpu 64 bit stats (v2)) added a race on 32bit arches. We must use separate syncp for rx and tx path as they can be run at the same time on different cpus. Thus one sequence increment can be lost and readers spin forever. Signed-off-by: Eric Dumazet <edumazet at google.com> Cc: Stephen Hemminger

From: Eric Dumazet <edumazet at google.com> commit 3fa2a1df909 (virtio-net: per cpu 64 bit stats (v2)) added a race on 32bit arches. We must use separate syncp for rx and tx path as they can be run at the same time on different cpus. Thus one sequence increment can be lost and readers spin forever. Signed-off-by: Eric Dumazet <edumazet at google.com> Cc: Stephen Hemminger

...application learn that its memory got wiped? S2disk is an > > async operation and it can happen at any time during the task execution. > > So how does the application work to prevent from corrupted state - e.g. > > when suspended between two memory loads? > > You can do it seqlock-style, kind of - you reserve the first byte of > the page or so as a "is this page initialized" marker, and after every > read from the page, you do a compiler barrier and check whether that > byte has been cleared. This is certainly possible yet wery awkwar interface to use IMH...

...application learn that its memory got wiped? S2disk is an > > async operation and it can happen at any time during the task execution. > > So how does the application work to prevent from corrupted state - e.g. > > when suspended between two memory loads? > > You can do it seqlock-style, kind of - you reserve the first byte of > the page or so as a "is this page initialized" marker, and after every > read from the page, you do a compiler barrier and check whether that > byte has been cleared. This is certainly possible yet wery awkwar interface to use IMH...