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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