Re: [PATCH 5/8] flow: Make flow timer per-caller for thread safety

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Jun 16, 2026 at 07:10:49PM +0200, Laurent Vivier wrote:
> Move the static flow_timer_run variable out of flow.c and pass it as a
> parameter to flow_defer_handler().  This allows each caller to maintain
> its own timer state: each vhost-user queue pair worker uses the per-qpair
> context.
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>

LGTM

> ---
>  flow.c  | 11 +++++------
>  flow.h  |  2 +-
>  passt.c |  8 +++++---
>  3 files changed, 11 insertions(+), 10 deletions(-)
> 
> diff --git a/flow.c b/flow.c
> index 787a7139cfc1..08c7620c7b0f 100644
> --- a/flow.c
> +++ b/flow.c
> @@ -142,9 +142,6 @@ static flow_sidx_t flow_hashtab[FLOW_HASH_SIZE];
>  static_assert(ARRAY_SIZE(flow_hashtab) >= 2 * FLOW_MAX,
>  "Safe linear probing requires hash table with more entries than the number of sides in the flow table");
>  
> -/* Last time the flow timers ran */
> -static struct timespec flow_timer_run;
> -
>  /** flowside_from_af() - Initialise flowside from addresses
>   * @side:	flowside to initialise
>   * @af:		Address family (AF_INET or AF_INET6)
> @@ -898,9 +895,11 @@ flow_sidx_t flow_lookup_sa(const struct ctx *c, uint8_t proto, uint8_t pif,
>   * flow_defer_handler() - Handler for per-flow deferred and timed tasks
>   * @c:		Execution context
>   * @now:	Current timestamp
> + * @timer_run:	Last time the flow timers ran
> + * @qpair:	Queue pair to process
>   */
>  void flow_defer_handler(const struct ctx *c, const struct timespec *now,
> -			unsigned int qpair)
> +			struct timespec *timer_run, unsigned int qpair)
>  {
>  	struct flow_free_cluster *free_head = NULL;
>  	unsigned *last_next = &flow_first_free;
> @@ -908,9 +907,9 @@ void flow_defer_handler(const struct ctx *c, const struct timespec *now,
>  	bool timer = false;
>  	union flow *flow;
>  
> -	if (timespec_diff_ms(now, &flow_timer_run) >= FLOW_TIMER_INTERVAL) {
> +	if (timespec_diff_ms(now, timer_run) >= FLOW_TIMER_INTERVAL) {
>  		timer = true;
> -		flow_timer_run = *now;
> +		*timer_run = *now;
>  	}
>  
>  	assert(!flow_new_entry); /* Incomplete flow at end of cycle */
> diff --git a/flow.h b/flow.h
> index 53e0408a9ee5..10634e64a7fc 100644
> --- a/flow.h
> +++ b/flow.h
> @@ -280,7 +280,7 @@ void flow_migrate(struct flow_common *f, unsigned int qpair, uint32_t events,
>  	(flow_migrate(&(flow_)->f, qpair_, events_, fd_, sidei_))
>  
>  void flow_defer_handler(const struct ctx *c, const struct timespec *now,
> -			unsigned int qpair);
> +			struct timespec *timer_run, unsigned int qpair);
>  int flow_migrate_source_early(struct ctx *c, const struct migrate_stage *stage,
>  			      int fd);
>  int flow_migrate_source_pre(struct ctx *c, const struct migrate_stage *stage,
> diff --git a/passt.c b/passt.c
> index 3afc59b19120..bebc2b99f523 100644
> --- a/passt.c
> +++ b/passt.c
> @@ -98,15 +98,16 @@ struct passt_stats {
>   * post_handler() - Run periodic and deferred tasks for L4 protocol handlers
>   * @c:		Execution context
>   * @now:	Current timestamp
> + * @timer_run:	Last time the flow timers ran
>   * @qpair:	Queue pair to process
>   */
>  static void post_handler(struct ctx *c, const struct timespec *now,
> -			 unsigned int qpair)
> +			 struct timespec *timer_run, unsigned int qpair)
>  {
>  	if (!c->no_tcp)
>  		tcp_defer_handler(c, now, qpair);
>  
> -	flow_defer_handler(c, now, qpair);
> +	flow_defer_handler(c, now, timer_run, qpair);
>  	fwd_scan_ports_timer(c, now);
>  
>  	if (!c->no_ndp)
> @@ -221,6 +222,7 @@ static void print_stats(const struct ctx *c, const struct passt_stats *stats,
>  static void passt_worker(void *opaque, int nfds, struct epoll_event *events)
>  {
>  	static struct passt_stats stats = { 0 };
> +	static struct timespec flow_timer_run;
>  	struct ctx *c = opaque;
>  	struct timespec now;
>  	int i;
> @@ -304,7 +306,7 @@ static void passt_worker(void *opaque, int nfds, struct epoll_event *events)
>  		print_stats(c, &stats, &now);
>  	}
>  
> -	post_handler(c, &now, QPAIR_DEFAULT);
> +	post_handler(c, &now, &flow_timer_run, QPAIR_DEFAULT);
>  
>  	migrate_handler(c);
>  }
> -- 
> 2.54.0
> 

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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