Date: Thu, 25 Aug 2016 16:36:37 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-threads@FreeBSD.org Subject: [Bug 211947] bconsole won't die sitting on do_rw_wrlock Message-ID: <bug-211947-16-vK3Is20tCK@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-211947-16@https.bugs.freebsd.org/bugzilla/> References: <bug-211947-16@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D211947 --- Comment #7 from commit-hook@freebsd.org --- A commit references this bug: Author: kib Date: Thu Aug 25 16:35:42 UTC 2016 New revision: 304808 URL: https://svnweb.freebsd.org/changeset/base/304808 Log: Prevent leak of URWLOCK_READ_WAITERS flag for urwlocks. If there was some error, e.g. the sleep was interrupted, as in the referenced PR, do_rw_rdlock() did not cleared URWLOCK_READ_WAITERS. Since unlock only wakes up write waiters when there is no read waiters, for URWLOCK_PREFER_READER kind of locks, the result was missed wakeups for writers. In particular, the most visible victims are ld-elf.so locks in processes which loaded libthr, because rtld locks are urwlocks in prefer-reader mode. Normal rwlocks fall into prefer-reader mode only if thread already owns rw lock in read mode, which is not typical and correspondingly less visible. In the PR, unowned rtld bind lock was waited for in the process where only one thread was left alive. Note that do_rw_wrlock() correctly clears URWLOCK_WRITE_WAITERS in case of errors. Reported and tested by: longwitz@incore.de PR: 211947 Sponsored by: The FreeBSD Foundation MFC after: 1 week Changes: head/sys/kern/kern_umtx.c --=20 You are receiving this mail because: You are the assignee for the bug.=
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