On Tue, Sep 24, 2013 at 09:19:49PM +0200, Jilles Tjoelker wrote: > On Tue, Sep 24, 2013 at 12:37:30AM +0300, Konstantin Belousov wrote: > > On Mon, Sep 23, 2013 at 10:26:13PM +0200, Tijl Coosemans wrote: > > > Has anyone taken a look at this PR yet? > > > > http://www.freebsd.org/cgi/query-pr.cgi?pr=182161 > > > This looks like a valid bug, but probably not a valid testcase. > > > Let me elaborate. When a signal is delivered, return from the signal > > handler is performed by the sigreturn(2), which reloads the whole > > register file when crossing kernel->user boundary due to sys_sigreturn(9) > > setting PCB_FULL_IRET flag. As result, the whole trap frame at the > > time of the syscall entry is restored, and ERESTART return is not > > exercised. > > > I was not able to reproduce the issue with the supplied test program > > on HEAD. I suspect that the program actually exposed the bug in the > > signal delivery in the threaded processes, which I introduced for 9.1 > > and fixed in r251047 & r251365. > > The ERESTART return happens if there is no signal or no longer a signal. > The latter is how the bug in the PR occurs: a SIGCHLD delivery via > handler in one thread races with a SIGCHLD acceptance in wait4() in > another thread. Note wait4() returning a value in the other thread in > the fourth line of the kdump output in the PR. > > For some reason, I can reproduce this easily on my local quad-core > r255729 stable/9 system but not on ref9-amd64.freebsd.org or > ref10-amd64.freebsd.org. > > I can also reproduce the bug on my local system by racing signal > delivery via handler with acceptance in sigtimedwait(). So, could you, please, check the r255844 on your machine ?
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