Date: Thu, 16 May 2019 13:03:55 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r347690 - head/sys/kern Message-ID: <201905161303.x4GD3tT2061069@repo.freebsd.org>
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Author: kib Date: Thu May 16 13:03:54 2019 New Revision: 347690 URL: https://svnweb.freebsd.org/changeset/base/347690 Log: imgact_elf.c: Add comment explaining the malloc/VOP_UNLOCK() dance from r347148. Requested by: alc Sponsored by: The FreeBSD Foundation MFC after: 3 days Modified: head/sys/kern/imgact_elf.c Modified: head/sys/kern/imgact_elf.c ============================================================================== --- head/sys/kern/imgact_elf.c Thu May 16 13:00:35 2019 (r347689) +++ head/sys/kern/imgact_elf.c Thu May 16 13:03:54 2019 (r347690) @@ -935,12 +935,22 @@ __elfN(get_interp)(struct image_params *imgp, const El interp_name_len = phdr->p_filesz; if (phdr->p_offset > PAGE_SIZE || interp_name_len > PAGE_SIZE - phdr->p_offset) { + /* + * The vnode lock might be needed by pagedaemon to + * clean pages owned by the vnode. Do not allow sleep + * waiting for memory with the vnode locked, instead + * try non-sleepable allocation first, and if it + * fails, go to the slow path were we drop the lock + * and do M_WAITOK. Text reference prevents + * modifications of the vnode content. + */ interp = malloc(interp_name_len + 1, M_TEMP, M_NOWAIT); if (interp == NULL) { VOP_UNLOCK(imgp->vp, 0); interp = malloc(interp_name_len + 1, M_TEMP, M_WAITOK); vn_lock(imgp->vp, LK_SHARED | LK_RETRY); } + error = vn_rdwr(UIO_READ, imgp->vp, interp, interp_name_len, phdr->p_offset, UIO_SYSSPACE, IO_NODELOCKED, td->td_ucred,
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