Author: jtl Date: Wed Mar 21 15:54:46 2018 New Revision: 331309 URL: https://svnweb.freebsd.org/changeset/base/331309
Log: If the INP lock is uncontested, avoid taking a reference and jumping through the lock-switching hoops. A few of the INP lookup operations that lock INPs after the lookup do so using this mechanism (to maintain lock ordering): 1. Lock lookup structure. 2. Find INP. 3. Acquire reference on INP. 4. Drop lock on lookup structure. 5. Acquire INP lock. 6. Drop reference on INP. This change provides a slightly shorter path for cases where the INP lock is uncontested: 1. Lock lookup structure. 2. Find INP. 3. Try to acquire the INP lock. 4. If successful, drop lock on lookup structure. Of course, if the INP lock is contested, the functions will need to revert to the previous way of switching locks safely. This saves a few atomic operations when the INP lock is uncontested. Discussed with: gallatin, rrs, rwatson MFC after: 2 weeks Sponsored by: Netflix, Inc. Differential Revision: https://reviews.freebsd.org/D12911 Modified: head/sys/netinet/in_pcb.c head/sys/netinet6/in6_pcb.c Modified: head/sys/netinet/in_pcb.c ============================================================================== --- head/sys/netinet/in_pcb.c Wed Mar 21 15:43:57 2018 (r331308) +++ head/sys/netinet/in_pcb.c Wed Mar 21 15:54:46 2018 (r331309) @@ -1632,6 +1632,7 @@ in_pcblookup_group(struct inpcbinfo *pcbinfo, struct i struct inpcbhead *head; struct inpcb *inp, *tmpinp; u_short fport = fport_arg, lport = lport_arg; + bool locked; /* * First look for an exact match. @@ -1818,18 +1819,32 @@ in_pcblookup_group(struct inpcbinfo *pcbinfo, struct i return (NULL); found: - in_pcbref(inp); - INP_GROUP_UNLOCK(pcbgroup); - if (lookupflags & INPLOOKUP_WLOCKPCB) { - INP_WLOCK(inp); - if (in_pcbrele_wlocked(inp)) - return (NULL); - } else if (lookupflags & INPLOOKUP_RLOCKPCB) { - INP_RLOCK(inp); - if (in_pcbrele_rlocked(inp)) - return (NULL); - } else + if (lookupflags & INPLOOKUP_WLOCKPCB) + locked = TRY_INP_WLOCK(inp); + else if (lookupflags & INPLOOKUP_RLOCKPCB) + locked = TRY_INP_RLOCK(inp); + else panic("%s: locking bug", __func__); + if (!locked) + in_pcbref(inp); + INP_GROUP_UNLOCK(pcbgroup); + if (!locked) { + if (lookupflags & INPLOOKUP_WLOCKPCB) { + INP_WLOCK(inp); + if (in_pcbrele_wlocked(inp)) + return (NULL); + } else { + INP_RLOCK(inp); + if (in_pcbrele_rlocked(inp)) + return (NULL); + } + } +#ifdef INVARIANTS + if (lookupflags & INPLOOKUP_WLOCKPCB) + INP_WLOCK_ASSERT(inp); + else + INP_RLOCK_ASSERT(inp); +#endif return (inp); } #endif /* PCBGROUP */ @@ -1968,23 +1983,38 @@ in_pcblookup_hash(struct inpcbinfo *pcbinfo, struct in struct ifnet *ifp) { struct inpcb *inp; + bool locked; INP_HASH_RLOCK(pcbinfo); inp = in_pcblookup_hash_locked(pcbinfo, faddr, fport, laddr, lport, (lookupflags & ~(INPLOOKUP_RLOCKPCB | INPLOOKUP_WLOCKPCB)), ifp); if (inp != NULL) { - in_pcbref(inp); - INP_HASH_RUNLOCK(pcbinfo); - if (lookupflags & INPLOOKUP_WLOCKPCB) { - INP_WLOCK(inp); - if (in_pcbrele_wlocked(inp)) - return (NULL); - } else if (lookupflags & INPLOOKUP_RLOCKPCB) { - INP_RLOCK(inp); - if (in_pcbrele_rlocked(inp)) - return (NULL); - } else + if (lookupflags & INPLOOKUP_WLOCKPCB) + locked = INP_TRY_WLOCK(inp); + else if (lookupflags & INPLOOKUP_RLOCKPCB) + locked = INP_TRY_RLOCK(inp); + else panic("%s: locking bug", __func__); + if (!locked) + in_pcbref(inp); + INP_HASH_RUNLOCK(pcbinfo); + if (!locked) { + if (lookupflags & INPLOOKUP_WLOCKPCB) { + INP_WLOCK(inp); + if (in_pcbrele_wlocked(inp)) + return (NULL); + } else { + INP_RLOCK(inp); + if (in_pcbrele_rlocked(inp)) + return (NULL); + } + } +#ifdef INVARIANTS + if (lookupflags & INPLOOKUP_WLOCKPCB) + INP_WLOCK_ASSERT(inp); + else + INP_RLOCK_ASSERT(inp); +#endif } else INP_HASH_RUNLOCK(pcbinfo); return (inp); Modified: head/sys/netinet6/in6_pcb.c ============================================================================== --- head/sys/netinet6/in6_pcb.c Wed Mar 21 15:43:57 2018 (r331308) +++ head/sys/netinet6/in6_pcb.c Wed Mar 21 15:54:46 2018 (r331309) @@ -868,6 +868,7 @@ in6_pcblookup_group(struct inpcbinfo *pcbinfo, struct struct inpcbhead *head; struct inpcb *inp, *tmpinp; u_short fport = fport_arg, lport = lport_arg; + bool locked; /* * First look for an exact match. @@ -1026,18 +1027,32 @@ in6_pcblookup_group(struct inpcbinfo *pcbinfo, struct return (NULL); found: - in_pcbref(inp); - INP_GROUP_UNLOCK(pcbgroup); - if (lookupflags & INPLOOKUP_WLOCKPCB) { - INP_WLOCK(inp); - if (in_pcbrele_wlocked(inp)) - return (NULL); - } else if (lookupflags & INPLOOKUP_RLOCKPCB) { - INP_RLOCK(inp); - if (in_pcbrele_rlocked(inp)) - return (NULL); - } else + if (lookupflags & INPLOOKUP_WLOCKPCB) + locked = INP_TRY_WLOCK(inp); + else if (lookupflags & INPLOOKUP_RLOCKPCB) + locked = INP_TRY_RLOCK(inp); + else panic("%s: locking buf", __func__); + if (!locked) + in_pcbref(inp); + INP_GROUP_UNLOCK(pcbgroup); + if (!locked) { + if (lookupflags & INPLOOKUP_WLOCKPCB) { + INP_WLOCK(inp); + if (in_pcbrele_wlocked(inp)) + return (NULL); + } else { + INP_RLOCK(inp); + if (in_pcbrele_rlocked(inp)) + return (NULL); + } + } +#ifdef INVARIANTS + if (lookupflags & INPLOOKUP_WLOCKPCB) + INP_WLOCK_ASSERT(inp); + else + INP_RLOCK_ASSERT(inp); +#endif return (inp); } #endif /* PCBGROUP */ @@ -1163,23 +1178,38 @@ in6_pcblookup_hash(struct inpcbinfo *pcbinfo, struct i struct ifnet *ifp) { struct inpcb *inp; + bool locked; INP_HASH_RLOCK(pcbinfo); inp = in6_pcblookup_hash_locked(pcbinfo, faddr, fport, laddr, lport, (lookupflags & ~(INPLOOKUP_RLOCKPCB | INPLOOKUP_WLOCKPCB)), ifp); if (inp != NULL) { - in_pcbref(inp); - INP_HASH_RUNLOCK(pcbinfo); - if (lookupflags & INPLOOKUP_WLOCKPCB) { - INP_WLOCK(inp); - if (in_pcbrele_wlocked(inp)) - return (NULL); - } else if (lookupflags & INPLOOKUP_RLOCKPCB) { - INP_RLOCK(inp); - if (in_pcbrele_rlocked(inp)) - return (NULL); - } else + if (lookupflags & INPLOOKUP_WLOCKPCB) + locked = INP_TRY_WLOCK(inp); + else if (lookupflags & INPLOOKUP_RLOCKPCB) + locked = INP_TRY_RLOCK(inp); + else panic("%s: locking bug", __func__); + if (!locked) + in_pcbref(inp); + INP_HASH_RUNLOCK(pcbinfo); + if (!locked) { + if (lookupflags & INPLOOKUP_WLOCKPCB) { + INP_WLOCK(inp); + if (in_pcbrele_wlocked(inp)) + return (NULL); + } else { + INP_RLOCK(inp); + if (in_pcbrele_rlocked(inp)) + return (NULL); + } + } +#ifdef INVARIANTS + if (lookupflags & INPLOOKUP_WLOCKPCB) + INP_WLOCK_ASSERT(inp); + else + INP_RLOCK_ASSERT(inp); +#endif } else INP_HASH_RUNLOCK(pcbinfo); return (inp); _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
