Date: Tue, 7 Sep 2010 00:23:45 +0000 (UTC) From: Ryan Stone <rstone@FreeBSD.org> To: cvs-src-old@freebsd.org Subject: cvs commit: src/sys/vm vm_mmap.c Message-ID: <201009070023.o870Ntu4066626@repoman.freebsd.org>
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rstone 2010-09-07 00:23:45 UTC
FreeBSD src repository
Modified files:
sys/vm vm_mmap.c
Log:
SVN rev 212281 on 2010-09-07 00:23:45Z by rstone
In munmap() downgrade the vm_map_lock to a read lock before taking a read
lock on the pmc-sx lock. This prevents a deadlock with
pmc_log_process_mappings, which has an exclusive lock on pmc-sx and tries
to get a read lock on a vm_map. Downgrading the vm_map_lock in munmap
allows pmc_log_process_mappings to continue, preventing the deadlock.
Without this change I could cause a deadlock on a multicore 8.1-RELEASE
system by having one thread constantly mmap'ing and then munmap'ing a
PROT_EXEC mapping in a loop while I repeatedly invoked and stopped pmcstat
in system-wide sampling mode.
Reviewed by: fabient
Approved by: emaste (mentor)
MFC after: 2 weeks
Revision Changes Path
1.245 +11 -3 src/sys/vm/vm_mmap.c
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