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    SubjectRe: nanosleep interrupted by ignored signals
    On Wed, Nov 24, 2004 at 07:06:27PM -0800, Matt Mackall wrote:
    > On Wed, Nov 24, 2004 at 06:45:05PM -0800, George Anzinger wrote:
    > > Matt Mackall wrote:
    > > >Take the following trivial program:
    > > >
    > > >#include <unistd.h>
    > > >
    > > >int main(void)
    > > >{
    > > > sleep(10);
    > > > return 0;
    > > >}
    > > >
    > > >Run it in an xterm. Note that resizing the xterm has no effect on the
    > > >process. Now do the same with strace:
    > > >
    > > >brk(0x80495bc) = 0x80495bc
    > > >brk(0x804a000) = 0x804a000
    > > >rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
    > > >rt_sigaction(SIGCHLD, NULL, {SIG_DFL}, 8) = 0
    > > >rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
    > > >nanosleep({10, 0}, 0xbffff548) = -1 EINTR (Interrupted system
    > > >call)
    > > >--- SIGWINCH (Window changed) ---
    > > >_exit(0) = ?
    > > >
    > > >In short, nanosleep is getting interrupted by signals that are
    > > >supposedly ignored when a process is being praced. This appears to be
    > > >a long-standing bug.
    > > >
    > > >It also appears to be a long-known bug. I found some old discussion of this
    > > >problem here but no sign of any resolution:
    > > >
    > > >http://www.ussg.iu.edu/hypermail/linux/kernel/0108.1/1448.html
    > > >
    > > >What's the current thinking on this?
    > >
    > > This should have been resolved with the 2.6 changes, in particular, the
    > > restart code. What kernel are you using?
    >
    > Indeed it is. Forgot I still had 2.4 on the box in question, didn't
    > notice the restart bit when comparing the 2.6 code against the thread
    > above. Mea culpa.

    George,

    Is it worth/necessary to fix this bug in v2.4 ?

    Quoting yourself

    "This is an issue for debugging also (same ptrace...). The fix is to fix
    nano_sleep to match the standard which says it should only return on a
    signal if the signal is delivered to the program (i.e. not on internal
    "do nothing" signals). Signal in the kernel returns 1 if it calls the
    task and 0 otherwise, thus nano sleep might be changed as follows: "


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