Hi John, On 10/06/15 17:32, John Baldwin wrote: > On 6/10/15 4:43 PM, Julien Charbon wrote: >> Author: jch >> Date: Wed Jun 10 20:43:07 2015 >> New Revision: 284245 >> URL: https://svnweb.freebsd.org/changeset/base/284245 >> >> Log: >> Fix a callout race condition introduced in TCP timers callouts with >> r281599. >> In TCP timer context, it is not enough to check callout_stop() return value >> to decide if a callout is still running or not, previous callout_reset() >> return values have also to be checked. >> >> Differential Revision: https://reviews.freebsd.org/D2763 >> Reviewed by: hiren >> Approved by: hiren >> MFC after: 1 day >> Sponsored by: Verisign, Inc. >> >> Modified: >> head/sys/netinet/tcp_timer.c >> head/sys/netinet/tcp_timer.h >> >> Modified: head/sys/netinet/tcp_timer.c >> ============================================================================== >> --- head/sys/netinet/tcp_timer.c Wed Jun 10 20:11:28 2015 >> (r284244) >> +++ head/sys/netinet/tcp_timer.c Wed Jun 10 20:43:07 2015 >> (r284245) >> @@ -347,11 +347,12 @@ tcp_timer_2msl(void *xtp) >> tp = tcp_close(tp); >> } else { >> if (tp->t_state != TCPS_TIME_WAIT && >> - ticks - tp->t_rcvtime <= TP_MAXIDLE(tp)) >> - callout_reset_on(&tp->t_timers->tt_2msl, >> - TP_KEEPINTVL(tp), tcp_timer_2msl, tp, >> - inp_to_cpuid(inp)); >> - else >> + ticks - tp->t_rcvtime <= TP_MAXIDLE(tp)) { >> + if (!callout_reset(&tp->t_timers->tt_2msl, >> + TP_KEEPINTVL(tp), tcp_timer_2msl, tp)) { >> + tp->t_timers->tt_flags &= ~TT_2MSL_RST; >> + } >> + } else >> tp = tcp_close(tp); > > Did you mean to use callout_reset() instead of callout_reset_on() here and > elsewhere in this change?
Thanks for this question. Exactly, the goal here is to make clear that once a TCP timer callout is scheduled on a core, we always reset this callout on the same core. It was already the case before, but having only one callout_reset_on() call in tcp_timer_activate() when we start callout the first time, and callout_reset() calls everywhere else make it (hopefully) clearer. My 2 cents. -- Julien
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