fd: stop looping in pwd_hold
We don't expect to fail acquiring the reference unless running into a corner case. Just in case ensure forward progress by taking the lock. Reviewed by: kib, markj Differential Revision: https://reviews.freebsd.org/D25616
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Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=363112
@ -3347,13 +3347,17 @@ pwd_hold(struct thread *td)
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fdp = td->td_proc->p_fd;
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smr_enter(pwd_smr);
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for (;;) {
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pwd = smr_entered_load(&fdp->fd_pwd, pwd_smr);
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MPASS(pwd != NULL);
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if (refcount_acquire_if_not_zero(&pwd->pwd_refcount))
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break;
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if (__predict_true(refcount_acquire_if_not_zero(&pwd->pwd_refcount))) {
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smr_exit(pwd_smr);
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return (pwd);
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}
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smr_exit(pwd_smr);
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FILEDESC_SLOCK(fdp);
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pwd = pwd_hold_filedesc(fdp);
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MPASS(pwd != NULL);
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FILEDESC_SUNLOCK(fdp);
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return (pwd);
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}
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