FreeBSD src
1321c5029e
Unlike buf_ring_peek, it only supports single consumer mode, and it clears the cons_head if DEBUG_BUFRING/INVARIANTS is defined. The normal use case of drbr_peek for network drivers is: m = drbr_peek(br); err = hw_spec_encap(&m); /* could m_defrag/m_collapse */ (*) if (err) { if (m == NULL) drbr_advance(br); else drbr_putback(br, m); /* break the loop */ } drbr_advance(br); The race is: If hw_spec_encap() m_defrag or m_collapse the mbuf, i.e. the old mbuf was freed, or like the Hyper-V's network driver, that transmission- done does not even require the TX lock; then on the other CPU at the (*) time, the freed mbuf could be recycled and being drbr_enqueue even before the current CPU had the chance to call drbr_{advance,putback}. This triggers a panic in drbr_enqueue duplicated element check, if DEBUG_BUFRING/INVARIANTS is defined. Use buf_ring_peek_clear_sc() in drbr_peek() to fix the above race. This change is a NO-OP, if neither DEBUG_BUFRING nor INVARIANTS are defined. MFC after: 1 week Sponsored by: Microsoft OSTC Differential Revision: https://reviews.freebsd.org/D5416 |
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bin | ||
cddl | ||
contrib | ||
crypto | ||
etc | ||
gnu | ||
include | ||
kerberos5 | ||
lib | ||
libexec | ||
release | ||
rescue | ||
sbin | ||
secure | ||
share | ||
sys | ||
targets | ||
tests | ||
tools | ||
usr.bin | ||
usr.sbin | ||
.arcconfig | ||
.arclint | ||
COPYRIGHT | ||
LOCKS | ||
MAINTAINERS | ||
Makefile | ||
Makefile.inc1 | ||
ObsoleteFiles.inc | ||
README | ||
UPDATING |
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